Polymerization catalysts for producing polymers with low melt elasticity

ABSTRACT

The present techniques relate to catalyst compositions, methods, and polymers encompassing a Group 4 metallocene compound comprising bridging η 5 -cyclopentadienyl-type ligands, typically in combination with a cocatalyst, and a activator. The compositions and methods presented herein include ethylene polymers with low melt elasticity.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/349,484, now U.S. Pat. No. 8,450,437, entitled “PolymerizationCatalysts for Producing Polymers With Low Melt Elasticity” filed on Jan.12, 2012, which is a divisional of U.S. patent application Ser. No.11/904,735, now U.S. Pat. No. 8,119,553, entitled “PolymerizationCatalysts for Producing Polymers With Low Melt Elasticity” filed on Sep.28, 2007, both of which are incorporated by reference herein in theirentirety for all purposes.

BACKGROUND OF THE INVENTION

The present techniques relate to the field of organometalliccompositions, olefin polymerization catalyst compositions, and methodsfor the polymerization and copolymerization of olefins using a catalystcomposition.

This section is intended to introduce the reader to aspects of art thatmay be related to aspects of the present techniques, which are describedand/or claimed below. Accordingly, it should be understood that thesestatements are to be read in this light, and not as admissions of priorart.

Polyolefins can be made using catalysts and various types ofpolymerization reactors that cause the combination of various monomers,such as alpha olefins, into chains of polymer. These alpha olefins areobtained from processing hydrocarbons, such as oil, into variouspetrochemicals. Different properties may be obtained if two or moredifferent alpha-olefin monomers are polymerized to form a copolymer. Ifthe same alpha-olefin is used for polymerization, the polymer can bereferred to as a homopolymer. As these polymer chains are developedduring polymerization, they can form solid particles, such as fluff orgranules, which possess certain properties and impart various mechanicaland physical properties to end products comprising these polymers.

Products made from polyolefins have become increasingly prevalent insociety as plastic products. One benefit of these polyolefins is thatthey are generally non-reactive when put in contact with various goodsor products. In particular, plastic products from polyolefin polymers(such as polyethylene, polypropylene, and their copolymers) are used forretail and pharmaceutical packaging (such as display bags, bottles, andmedication containers), food and beverage packaging (such as juice andsoda bottles), household and industrial containers (such as pails, drumsand boxes), household items (such as appliances, furniture, carpeting,and toys), automobile components, fluid, gas and electrical conductionproducts (such as cable wrap, pipes, and conduits), and various otherindustrial and consumer products.

Many methods are used for the manufacture of products from polyolefins,including but not limited to, blow-molding injection-molding, rotationalmolding, various extrusion methods, thermoforming, sheet molding andcasting. The mechanical requirements of the end-product application,such as tensile strength and density, and/or the chemical requirements,such as thermal stability, molecular weight, and chemical reactivity,typically determine what type of polyolefin is suitable and provides thebest processing capabilities during manufacture.

BRIEF DESCRIPTION OF THE FIGURES

Advantages of the techniques may become apparent upon reading thefollowing detailed description and upon reference to the drawings inwhich:

FIG. 1 represents the chemical structures of exemplary metallocenes inaccordance with embodiments of the present techniques;

FIG. 2 represents the chemical structures of reference metallocenes; and

FIG. 3 represents a log-log graph of tan δ vs. molecular weight, asobtained from rheological measurements made on the exemplary ethylenehomopolymers described in Examples 3-24.

DETAILED DESCRIPTION

Catalysts that may be used in the polymerization of olefin monomer topolyolefin, e.g., ethylene to polyethylene, include organometalliccomplexes, such as organic compounds containing metal atoms, such astitanium, zirconium, vanadium, chromium, and so on. Duringpolymerization, these catalysts temporarily attach to the monomer toform an active center that facilitates the sequential addition ofmonomer units to form the longer polymer chains. The catalysts can becombined with a support or activator-support (e.g., a solid oxide). Inaddition, the metal catalyst and solid oxide may be blended with acocatalyst to further activate the catalyst for polymerization. Catalystcompositions of organometallic complexes may be useful both forhomopolymerization of ethylene and for copolymerization of ethylene withcomonomers such as propylene, 1-butene, 1-hexene, or other higherα-olefins.

Polyethylene (PE) produced by any number of these organometalliccatalyst compositions generally has low melt elasticity. Melt elasticitymay be considered as the tendency of a molten polymer to flex ordistort. While in some circumstances, melt elasticity may be useful,such as for improving bubble stability during the formation of blownfilm, in some cases melt elasticity causes less than ideal processingcapabilities. For example, melt elasticity may be associated with filmorientation, melt fracture, and haze. A polymer that has high meltelasticity may develop significant orientation during blown filmprocessing, leading to anisotropic properties. In such a film, the tearstrength may be too low in one direction. In other cases, a polymer withhigh melt elasticity may exhibit severe melt fracturing, in which thepolymer has a very irregular or distorted flow during extrusion from adie face, leading to uneven shapes or surface irregularities. In certaincases, the polymer flow may even be interrupted, as the polymerextrudate breaks when it is stretched from the face of the die. Even inless severe cases, melt elasticity may contribute to irregular flowduring processing, giving a high surface haze to the finished article.

One of the organometallic complex catalyst systems to be developed inrecent years has a metal center attached to a 5-member carbon ring.These systems are called metallocenes. One common type of metallocenesystem has a bridging group connecting two five membered rings, whichare attached to each side of a metal atom to form a sandwich type ofstructure. These are termed bridging or ansa-metallocenes. Whilemetallocene systems may be more active than other types of catalysts,and ansa-metallocenes may form desirable catalysts for some purposes,they may tend to produce polymer with high melt elasticity which, asdiscussed above, may not provide the best film performance.

A further challenge in the development of metallocene systems for thepolymerization of ethylene is the production of high molecular weightresins. Some metallocene systems may produce resins with lower molecularweights than produced using other types of polyolefin polymerizationcatalysts. However, the high molecular weight resins produced with someof these other types of polymerization catalysts may display high meltelasticity, which may lead to undesirable film properties in certainproduct applications. Further, some of these other catalysts may be lessefficient at incorporating comonomers. In contrast, tightly bridgedmetallocenes offer excellent comonomer incorporation, but may stillgenerate resins having too high of a melt elasticity for the desiredproduct application. What is desirable for certain product applicationsis a catalyst system that will yield high molecular weight resins havinglow melt elasticity.

Metallocene catalyst systems offer a significant ability to tailorresins by combining multiple metallocene catalysts in a blended system.This ability to tailor resins may be useful in the production ofmulti-modal resins. For example, the physical properties of such resinblends may be enhanced by higher incorporation of comonomer in the highmolecular weight chains versus the lower molecular weight chains. Whenused in a mixed metallocene catalyst system, the single atom bridgedmetallocene catalysts of the present techniques may yield high molecularweight resins having low melt elasticity.

One or more specific embodiments of the present techniques will bedescribed below. In an effort to provide a concise description of theseembodiments, not all features of an actual implementation are describedin the specification. It should be appreciated that in the developmentof any such actual implementation, as in any engineering or designproject, numerous implementation-specific decisions must be made toachieve the developers' specific goals, such as compliance withsystem-related and business-related constraints, which may vary from oneimplementation to another. Moreover, it should be appreciated that sucha development effort might be complex and time consuming, but wouldnevertheless be a routine undertaking of design, fabrication, andmanufacture for those of ordinary skill having the benefit of thisdisclosure.

The present techniques include new catalyst compositions, methods forpreparing catalyst compositions, and methods for using the catalystcompositions to polymerize olefins. In some embodiments, the techniquesencompass a catalyst composition prepared by contacting atightly-bridged ansa-metallocene compound including an alkyl groupsubstituent on one of the cyclopentadienyl-type ligands, a supportand/or an activator-support, and optionally an organoaluminum compound.The catalyst composition formed as the contact product may include thecontacted compounds, reaction products formed from the contactedcompounds, or both. In other embodiments, the present techniques includemethods for making the catalyst composition presented herein, and in yetother embodiments, the present techniques include methods forpolymerizing olefins employing the catalyst composition presentedherein. As described above, the designation of the organoaluminumcompound as an optional component in the contact product is intended toreflect that the organoaluminum compound may be optional if it is notneeded to impart catalytic activity to the catalyst composition, forexample, when the metal center already has a single-bonded carbon groupas a ligand. To facilitate discussion of the current techniques, thediscussion contained herein is presented in sections.

Section I presents catalyst compositions and components in accordancewith embodiments of the present techniques. The catalyst compositionsand components include exemplary metallocene compounds, optionalorganoaluminum compounds, activators/cocatalysts, nonlimiting examplesof catalyst compositions, and olefin monomers that may be employed inthe present techniques.

Section II presents techniques for the preparation of exemplary catalystcompositions using the components discussed in Section I. Thesepreparations include the precontacting of the catalyst compositions witholefins, the use of multiple precontacting steps, the composition ratiosthat may be used in catalyst compositions of the present techniques,exemplary catalyst preparation processes, and the activities ofcatalysts (in terms of polymer produced per weight catalyst per hour)that may be obtained from the catalyst compositions of the presenttechniques.

Section III discusses various processes that the catalyst compositionsof the present techniques may be used in for polymerization. Particularprocesses discussed include loop slurry polymerizations, gas phasepolymerizations, and solution phase polymerizations. Other informationrelevant to the implementation of the catalyst compositions of thecurrent techniques is also presented in this section, including plantsystems for feed to and polymer removal from the reactors, particularpolymerization conditions, and exemplary products that may be made frompolymers formed using the catalyst compositions of the presenttechniques.

Section IV discloses non-limiting examples of polymers prepared usingcatalyst compositions in accordance with embodiments of the presenttechniques. The examples include data indicating the improvements inmelt elasticity that may be obtained for polymers made using exemplarycatalyst compositions of the present techniques. The results that may beobtained for molecular weights and catalyst activities using theexemplary catalyst compositions are also discussed.

Section V presents experimental procedures that may be used to make andtest exemplary catalyst compositions in accordance with embodiments ofthe present techniques. The techniques include a method that may be usedfor the determination of relative molecular weight using a standardgenerated from an absolute determination of molecular weight and atechnique for the absolute determination of molecular weight usingSEC-MALS. A method for the determination of pore size is discussed.Further, the section includes a discussion of a technique that may beused for the measurement of Tan δ, which was used to determine the meltelasticity. Section V also discusses exemplary techniques for synthesisof the various polymer components. These procedures include techniquesfor making the fluorided silica-alumina and sulfated aluminaactivator-supports. The procedures also include techniques for makingexemplary metallocenes and polymers, in accordance with embodiments ofthe present techniques.

I. Catalyst Composition and Components

A. The Metallocene Compounds

1. Overview

The catalyst compositions of the present techniques may include atightly-bridged ansa-metallocene compound that has an alkyl group ofthree to 20 carbons bonded to a η⁵-cyclopentadienyl-type ligand (suchas, for example, a cyclopentadienyl, an indenyl, or a fluorenyl). Thecatalyst compositions may also include an activator, and, optionally, anorganoaluminum compound as further described below. A generaldescription of the ansa-metallocene complex is presented in thefollowing subsection 2.

The term “bridged” or “ansa-metallocene” refers to a metallocenecompound in which the two η⁵-cycloalkadienyl-type ligands in themolecule are linked by a bridging moiety. Useful ansa-metallocenes maybe “tightly-bridged,” meaning that the two η⁵-cycloalkadienyl-typeligands are connected by a bridging group wherein the shortest link ofthe bridging moiety between the η⁵-cycloalkadienyl-type ligands is asingle atom. The metallocenes described herein are therefore bridgedbis(η⁵-cycloalkadienyl)-type compounds. The bridging group may have theformula >ER¹R², wherein E may be a carbon atom, a silicon atom, agermanium atom, or a tin atom, and wherein R² is bonded to bothη⁵-cyclopentadienyl-type ligands. In this embodiment, R¹ and R² may beindependently an alkyl group or an aryl group, either of which having upto 12 carbon atoms, or hydrogen.

The bridging group, ER¹R², may be: >CR¹R², >SiR¹R², >GeR¹R², or >SnR¹R²,wherein R¹ and R² may be independently an alkyl group or an aryl group,(either of which may have up to 12 carbon atoms), or hydrogen. Suchbridging ER¹R² groups may include, for example, >CPh₂, >SiPh₂, >GePh₂,>SnPh₂, >C(tolyl)₂, >Si(tolyl)₂, >Ge(tolyl)₂,>Sn(tolyl)₂, >CMePh, >SiMePh, >GeMePh, >SnMePh, >CEtPh, >CPrPh, >CBuPh, >CMe(tolyl), >SiMe(tolyl), >GeMe(tolyl), >SnMe(tolyl), >CHPh,and >CH(tolyl), among others.

Further, one substituent on the η⁵-cyclopentadienyl-type ligands is asubstituted or an unsubstituted alkyl group, which may have up to 12carbon atoms. The complexes are discussed in the following subsection 3,and shown in the general structural formulas presented therein.Exemplary metallocene complexes, in accordance with embodiments of thepresent techniques are discussed in the following subsection 4 and shownin FIG. 1.

2. General Metallocene Formula

In embodiments of the present techniques, the ansa-metallocene of thepresent techniques may be expressed by the general formula:(X¹)(X²)(X³)(X⁴)M¹.In this formula, M¹ may be titanium, zirconium, or hafnium, X¹ may be asubstituted cyclopentadienyl, a substituted indenyl, or a substitutedfluorenyl. X² may be a substituted cyclopentadienyl or a substitutedfluorenyl. One substituent on X¹ and X² is a bridging group having theformula ER¹R². E may be a carbon atom, a silicon atom, a germanium atom,or a tin atom, and is bonded to both X¹ and X². R¹ and R² may beindependently an alkyl group or an aryl group, either of which may haveup to 12 carbon atoms, or may be hydrogen. The bridging groups may beselected to influence the activity of the catalyst or the structure ofthe polymer produced. One substituent on X² is a substituted or anunsubstituted alkyl group, which may have up to 12 carbon atoms.Substituents X³ and X⁴ may be independently: 1) F, Cl, Br, or I; 2) ahydrocarbyl group having up to 20 carbon atoms, H, or BH₄; 3) ahydrocarbyloxide group, a hydrocarbylamino group, or atrihydrocarbylsilyl group, any of which may have up to 20 carbon atoms;4) OBR^(A) ₂ or SO₃R^(A), wherein R^(A) may be an alkyl group or an arylgroup, either of which may have up to 12 carbon atoms. Any additionalsubstituent on the substituted cyclopentadienyl, substituted indenyl,substituted fluorenyl, or substituted alkyl group may be independentlyan aliphatic group, an aromatic group, a cyclic group, a combination ofaliphatic and cyclic groups, an oxygen group, a sulfur group, a nitrogengroup, a phosphorus group, an arsenic group, a carbon group, a silicongroup, or a boron group, any of which may have from 1 to 20 carbonatoms. Alternatively, additional substituents may be present, includinghalides or hydrogen. The substituents on the η⁵-cyclopentadienyl-typeligands may be used to control the activity of the catalyst or thestereochemistry of the polymer produced.

The alkyl group bonded to the η⁵-cyclopentadienyl-type ligands may haveup to about 20 carbon atoms, up to about 12 carbon atoms, up to about 8carbon atoms, or up to about 6 carbon atoms. Such alkyl groups mayinclude, for example, ethyl, propyl, butyl, pentyl, hexyl, heptyl, oroctyl, among others.

While an unsubstituted alkyl may be a substituent on theη⁵-cyclopentadienyl-type ligands, alternatively, the alkyl groupsubstituent may be further substituted. However, this furthersubstitution may lower the activity of the catalyst. Any substituentpresent may be selected independently from an aliphatic group, anaromatic group, a cyclic group, a combination of aliphatic and cyclicgroups, an oxygen group, a sulfur group, a nitrogen group, a phosphorusgroup, an arsenic group, a carbon group, a silicon group, a boron group,or a substituted analog thereof, any of which may have from 1 to about20 carbon atoms. The substituents may also include a halide or hydrogen.Further, this description of other substituents on the alkyl group atommay include substituted, unsubstituted, branched, linear, orheteroatom-substituted analogs of these moieties. Such alkyl groups mayinclude, for example, 3-methyl butyl [CH₂CH₂CH(CH₃)CH₃], 4-methylpentyl[CH₂CH₂CH₂CH(CH₃)₂, 1,1-dimethylbutyl [C(CH₃)₂CH₂CH₂CH₃], or1,1-dimethylpentyl[C(CH₃)₂CH₂CH₂CH₂CH₃], among others.

In addition to containing a bridging group having the formula ER¹R² andan alkyl group as described above, the η⁵-cyclopentadienyl-type ligandsmay also have other substituents. For example, these substituents may bethe same chemical groups or moieties that can serve as the X³ or X⁴ligands of the ansa-metallocenes. Thus, any additional substituent onthe η⁵-cyclopentadienyl-type ligands, the substituted alkyl group, X³,or X⁴ may be independently such groups as an aliphatic group, anaromatic group, a cyclic group, a combination of aliphatic and cyclicgroups, an oxygen group, a sulfur group, a nitrogen group, a phosphorusgroup, an arsenic group, a carbon group, a silicon group, a boron group,or a substituted analog thereof, any of which having from 1 to about 20carbon atoms. The substituents may also include a halide or hydrogen, aslong as these groups generally do not terminate the activity of thecatalyst composition. Further, this list may include substituents thatmay be characterized in more than one of these categories, such asbenzyl. Substituents may also include substituted indenyl andsubstituted fluorenyl, including partially saturated indenyls andfluorenyls such as, for example, tetrahydroindenyl groups,tetrahydrofluorenyl groups, and octahydrofluorenyl groups. These varioussubstituent groups are further discussed in the paragraphs that follow.

Aliphatic groups that may be used as substituents include, for example,an alkyl group, a cycloalkyl group, an alkenyl group, a cycloalkenylgroup, an alkynyl group, an alkadienyl group, a cyclic group, and thelike. This may include all substituted, unsubstituted, branched, andlinear analogs or derivatives thereof, wherein each group may have fromone to about 20 carbon atoms. Thus, aliphatic groups may include, forexample, hydrocarbyls such as paraffins and alkenyls. For example, thealiphatic groups may include such groups as methyl, ethyl, propyl,n-butyl, tert-butyl, sec-butyl, isobutyl, amyl, isoamyl, hexyl,cyclohexyl, heptyl, octyl, nonyl, decyl, dodecyl, 2-ethylhexyl,pentenyl, butenyl, and the like.

Aromatic groups that may be used as substituents include, for example,phenyl, naphthyl, anthracenyl, and the like. Substituted derivatives ofthese compounds are also included, wherein each group may have from 6 toabout 25 carbons. Such substituted derivatives may include, for example,tolyl, xylyl, mesityl, and the like, including heteroatom substitutedderivatives thereof.

Cyclic groups that may be used as substituents include, for example,cycloparaffins, cycloolefins, cycloacetylenes, arenes such as phenyl,bicyclic groups and the like, as well as substituted derivativesthereof, in each occurrence having from about 3 to about 20 carbonatoms. Thus, heteroatom-substituted cyclic groups such as furanyl may beincluded herein. Such substituents may include, aliphatic and cyclicgroups, e.g., groups that have both an aliphatic portion and a cyclicportion. Examples of these substituents may include groups such as:—(CH₂)_(m)C₆H_(q)R_(5-q) wherein m may be an integer from 1 to about 10,and q may be an integer from 1 to 5, inclusive;—(CH₂)_(m)C₆H_(q)R_(11-q) wherein m may be an integer from 1 to about10, and q may be an integer from 1 to 11, inclusive;—(CH₂)_(m)C₅H_(q)R_(9-q) wherein m may be an integer from 1 to about 10,and q may be an integer from 1 to 9, inclusive. As defined above, R maybe independently selected from: an aliphatic group; an aromatic group; acyclic group; any combination thereof; any substituted derivativethereof, including, but not limited to, a halide-, an alkoxide-, or anamide-substituted derivative or analog thereof; any of which has from 1to about 20 carbon atoms; or hydrogen. In various embodiments, suchaliphatic and cyclic groups may include, for example: —CH₂C₆H₅;—CH₂C₆H₄F; —CH₂C₆H₄Cl; —CH₂C₆H₄Br; —CH₂C₆H₄I; —CH₂C₆H₄OMe; —CH₂C₆H₄OEt;—CH₂C₆H₄NH₂; —CH₂C₆H₄NMe₂; —CH₂C₆H₄NEt₂; —CH₂CH₂C₆H₅; —CH₂CH₂C₆H₄F;—CH₂CH₂C₆H₄Cl; —CH₂CH₂C₆H₄Br; —CH₂CH₂C₆H₄I; —CH₂CH₂C₆H₄OMe;—CH₂CH₂C₆H₄OEt; —CH₂CH₂C₆H₄NH₂; —CH₂CH₂C₆H₄NMe₂; —CH₂CH₂C₆H₄NEt₂; anyregioisomer thereof, and any substituted derivative thereof.

Substituents may contain heteroatoms, including, for example, halides,oxygen, sulfur, nitrogen, phosphorous, or arsenic. Examples of halidesinclude fluoride, chloride, bromide, and iodide. As used herein, oxygengroups are oxygen-containing groups, including, for example, alkoxy oraryloxy groups (—OR) and the like, wherein R may be alkyl, cycloalkyl,aryl, aralkyl, substituted alkyl, substituted aryl, or substitutedaralkyl having from 1 to about 20 carbon atoms. Such alkoxy or aryloxygroups (—OR) groups may include, for example, methoxy, ethoxy, propoxy,butoxy, phenoxy, or substituted phenoxy, among others. As used herein,sulfur groups are sulfur-containing groups, including, for example, —SRand the like, wherein R may be alkyl, cycloalkyl, aryl, aralkyl,substituted alkyl, substituted aryl, or substituted aralkyl having from1 to about 20 carbon atoms. As used herein, nitrogen groups arenitrogen-containing groups, which may include, for example, —NR₂ orpyridyl groups, and the like, wherein R may be alkyl, cycloalkyl, aryl,aralkyl, substituted alkyl, substituted aryl, or substituted aralkylhaving from 1 to about 20 carbon atoms. As used herein, phosphorusgroups are phosphorus-containing groups, which may include, for example,—PR₂, and the like, wherein R may be alkyl, cycloalkyl, aryl, aralkyl,substituted alkyl, substituted aryl, or substituted aralkyl having from1 to about 20 carbon atoms. As used herein, arsenic groups arearsenic-containing groups, which may include, for example, —AsR₂, andthe like, wherein R may be alkyl, cycloalkyl, aryl, aralkyl, substitutedalkyl, substituted aryl, or substituted aralkyl having from 1 to about20 carbon atoms.

As used herein, carbon groups are carbon-containing groups, which mayinclude, for example, alkyl halide groups. Such alkyhalide groups mayinclude halide-substituted alkyl groups with 1 to about 20 carbon atoms,alkenyl or alkenyl halide groups with 1 to about 20 carbon atoms,aralkyl or aralkyl halide groups with 1 to about 20 carbon atoms, andthe like, including substituted derivatives thereof.

As used herein, silicon groups are silicon-containing groups, which mayinclude, for example, silyl groups such alkylsilyl groups, arylsilylgroups, arylalkylsilyl groups, siloxy groups, and the like, having from1 to about 20 carbon atoms. For example, silicon groups includetrimethylsilyl and phenyloctylsilyl groups.

As used herein, boron groups are boron-containing groups, which mayinclude, for example, —BR₂, —BX₂, —BRX, wherein X may be a monoanionicgroup such as halide, hydride, alkoxide, alkyl thiolate, and the. R maybe alkyl, cycloalkyl, aryl, aralkyl, substituted alkyl, substitutedaryl, or substituted aralkyl having from 1 to about 20 carbon atoms.

The remaining substituents on the metal center, X³ and X⁴, may beindependently an aliphatic group, a cyclic group, a combination of analiphatic group and a cyclic group, an amido group, a phosphido group,an alkyloxide group, an aryloxide group, an alkanesulfonate, anarenesulfonate, or a trialkylsilyl, or a substituted derivative thereof,any of which having from 1 to about 20 carbon atoms; or a halide. Morespecifically, X³ and X⁴ may be independently: 1) F, Cl, Br, or I; 2) ahydrocarbyl group having up to 20 carbon atoms, H, or BH₄; 3) ahydrocarbyloxide group, a hydrocarbylamino group, or atrihydrocarbylsilyl group, any of which having up to 20 carbon atoms; 4)OBR^(A) ₂ or SO₃R^(A), wherein R^(A) may be an alkyl group or an arylgroup, any of which having up to 12 carbon atoms.

3. General Structural Formulas for Metallocene Catalysts

Embodiments of the current techniques may include an ansa-metallocenehaving the general formula:

wherein M¹ may be zirconium or hafnium and X′ and X″ may beindependently F, Cl, Br, or I. E may be C or Si and R¹ and R² may beindependently an alkyl group or an aryl group, either of which may haveup to 10 carbon atoms, or R¹ and R² may be hydrogen. R^(3A) and R^(3B)may be independently a hydrocarbyl group or a trihydrocarbylsilyl group,any of which may have up to 20 carbon atoms, or may be hydrogen. Thesubscript ‘n’ may be an integer that may range from 0 to 10, inclusive.R^(4A) and R^(4B) may be independently a hydrocarbyl group that may haveup to 12 carbon atoms, or may be hydrogen.

In other embodiments, the ansa-metallocene may include a compound havingthe formula:

In this formula, M¹ may be zirconium or hafnium, and X′ and X″ may beindependently F, Cl, Br, or I. E may be C or Si and R¹ and R² may beindependently an alkyl group or an aryl group, either of which having upto 10 carbon atoms, or hydrogen. R^(3A) and R^(3B) may be independentlyH, methyl, allyl, benzyl, butyl, pentyl, hexyl, or trimethylsilyl, and‘n’ may be an integer from 1 to 6, inclusive. R^(4A) and R^(4B) may beindependently a hydrocarbyl group having up to 6 carbon atoms, orhydrogen.

In still other embodiments, the ansa-metallocene may include a compoundhaving the formula:

In this formula, M¹ may be zirconium or hafnium, and X′ and X″ may beindependently F, Cl, Br, or I. E may be C or Si and R¹ and R² may beindependently methyl or phenyl. R^(3A) and R^(3B) may be independently Hor methyl, and n may be 1 or 2. R^(4A) and R^(4B) may be independently Hor t-butyl.

In yet other embodiments, the ansa-metallocene of the present techniquesmay include a compound having the formula:

In this formula, M¹ may be zirconium or hafnium, and X′ and X″ may beindependently H, BH₄, methyl, phenyl, benzyl, neopentyl,trimethylsilylmethyl, CH₂CMe₂Ph; CH₂SiMe₂Ph; CH₂CMe₂CH₂Ph; orCH₂SiMe₂CH₂Ph. E may be C or Si and R¹ and R² may be independently analkyl group or an aryl group, either of which having up to 10 carbonatoms, or hydrogen. R^(3A) and R^(3B) may be independently a hydrocarbylgroup or a trihydrocarbylsilyl group, any of which having up to 20carbon atoms, or hydrogen, and n may be an integer from 0 to 10,inclusive. R^(4A) and R^(4B) may be independently a hydrocarbyl grouphaving up to 12 carbon atoms, or hydrogen.

4. Non-limiting Examples of Metallocene Structures

In exemplary embodiments, the ansa-metallocene may include any ofcompounds (I-1) through (I-4), as shown in FIG. 1, or any combinationthereof. Numerous processes to prepare metallocene compounds that may beemployed in the present techniques have been reported. For example, U.S.Pat. Nos. 4,939,217, 5,191,132, 5,210,352, 5,347,026, 5,399,636,5,401,817, 5,420,320, 5,436,305, 5,451,649, 5,496,781, 5,498,581,5,541,272, 5,554,795, 5,563,284, 5,565,592, 5,571,880, 5,594,078,5,631,203, 5,631,335, 5,654,454, 5,668,230, 5,705,578, 5,705,579,6,187,880, and 6,509,427 describe such methods, each of which isincorporated by reference in its entirety herein.

B. Optional Organoaluminum Compounds

In one embodiment, the present techniques may include a catalystcomposition including a tightly-bridged ansa-metallocene compound havingan alkyl moiety bonded to a η⁵-cyclopentadienyl-type ligand, a solidoxide activator-support, and, optionally, an organoaluminum compound.The designation of the organoaluminum compound as “optional” is intendedto reflect that the organoaluminum compound may be optional when it maynot be needed to impart catalytic activity to the catalyst composition.

Organoaluminum compounds that may be used in the present techniquesinclude, for example, compounds with the formula:Al(X⁵)_(n)(X⁶)_(3-n),wherein X⁵ may be a hydrocarbyl having from 1 to about 20 carbon atoms;X⁶ may be alkoxide or aryloxide, any of which having from 1 to about 20carbon atoms, halide, or hydride; and n may be a number from 1 to 3,inclusive. In various embodiments, X⁵ may be an alkyl having from 1 toabout 10 carbon atoms. Moieties used for X⁵ may include, for example,methyl, ethyl, propyl, butyl, sec-butyl, isobutyl, 1-hexyl, 2-hexyl,3-hexyl, isohexyl, heptyl, or octyl, and the like. In other embodiments,X⁶ may be independently fluoride, chloride, bromide, methoxide,ethoxide, or hydride. In yet another embodiment, X⁶ may be chloride.

In the formula Al(X⁵)_(n)(X⁶)_(3-n), n may be a number from 1 to 3inclusive, and in an exemplary embodiment, n is 3. The value of n is notrestricted to an integer, therefore this formula may includesesquihalide compounds, other organoaluminum cluster compounds, and thelike.

Generally, organoaluminum compounds that may be used in the presenttechniques may include trialkylaluminum compounds, dialkylaluminiumhalide compounds, dialkylaluminum alkoxide compounds, dialkylaluminumhydride compounds, and combinations thereof. Examples of suchorganoaluminum compounds include trimethylaluminum, triethylaluminum(TEA), tripropylaluminum, tributylaluminum, tri-n-butylaluminum (TNBA),triisobutylaluminum (TIBA), trihexylaluminum, triisohexylaluminum,trioctylaluminum, diethylaluminum ethoxide, diisobutylaluminum hydride,or diethylaluminum chloride, or any combination thereof. If theparticular alkyl isomer is not specified, the compound may encompass allisomers that can arise from a particular specified alkyl group.

In some embodiments, the present techniques may include precontactingthe ansa-metallocene with an organoaluminum compound and an olefinmonomer to form a precontacted mixture, prior to contacting thisprecontacted mixture with the solid oxide activator-support to form theactive catalyst. When the catalyst composition is prepared in thismanner, a portion of the organoaluminum compound may be added to theprecontacted mixture and another portion of the organoaluminum compoundmay be added to the postcontacted mixture prepared when the precontactedmixture is contacted with the solid oxide activator. However, all of theorganoaluminum compound may be employed to prepare the catalyst ineither the precontacting or postcontacting step. Alternatively, thesolid oxide may also be treated with aluminum alkyl before being treatedwith metallocene or other mixtures. These precontacting steps are notrequired, and all of the catalyst components may be contacted in asingle step.

Further, more than one organoaluminum compound may be used, in eitherthe precontacting or the postcontacting step, or in any procedure inwhich the catalyst components are contacted. When an organoaluminumcompound is added in multiple steps, the amounts of organoaluminumcompound presented herein include the total amount of organoaluminumcompound used in both the precontacted and postcontacted mixtures, andany additional organoaluminum compound added to the polymerizationreactor. Therefore, total amounts of organoaluminum compounds arepresented, regardless of whether a single organoaluminum compound isused, or more than one organoaluminum compound. Again, exemplaryorganoaluminum compounds used in embodiments of the present techniquesmay include, for example, triethylaluminum (TEA), tri-n-butylaluminum(TNBA), triisobutylaluminum (TIBA), and so on, or any combinationthereof.

C. The Activator/Cocatalyst

1. Overview

Embodiments of the present techniques encompass a catalyst compositionincluding: a tightly-bridged ansa-metallocene compound as presentedherein, optionally, an organoaluminum compound, and an activator. Theactivator may be required to weaken the bonds between the metal centerand ligands X³ or X⁴, discussed above, allowing complexation of themetal center with an olefin. Further, an activator or co-catalyst mayreplace X³ or X⁴ with a carbon group having a single-bond to the metal.The activator may be an activator-support including: a solid oxidetreated with an electron-withdrawing anion, as discussed in thefollowing subsection 2; an ion-exchangeable or layered mineralactivator-support, as discussed in the following subsection 3; anorganoaluminoxane compound, as discussed in the following subsection 4;an organoboron or organoborate compound, as discussed in the followingsubsection 5; or an ionizing compound, as discussed in the followingsubsection 6; or any combination of any of these activators.

In some embodiments, aluminoxane may not be required to form thecatalyst composition as presented herein, a feature that allows lowerpolymer production costs. Accordingly, AlR₃-type organoaluminumcompounds and one or more activator-supports may be used in the absenceof aluminoxanes. While not intending to be bound by theory, it isbelieved that the organoaluminum compounds may not activate themetallocene catalysts in the same manner as an organoaluminoxane.

Additionally, no borate compounds or MgCl₂ may be required to form thecatalyst composition of the present techniques, although aluminoxane,borate compounds, MgCl₂, or any combination thereof, may optionally beused in the catalyst composition of the present techniques. Further, insuch compounds as aluminoxanes, organoboron compounds, ionizing ioniccompounds, or any combination thereof, may be used as cocatalysts withthe ansa-metallocene, either in the presence or absence of the activatorsupport. Such cocatalysts may be used with the ansa-metallocene, eitherin the presence or absence of an organoaluminum compound, as specifiedherein. Thus, the organoaluminum compound is optional: when a ligand onthe metallocene is a hydrocarbyl group, H, or BH₄; when the activatorincludes an organoaluminoxane compound; or when both these conditionsare present. However, the catalyst compositions of the presenttechniques may be active in the substantial absence of cocatalysts suchas aluminoxanes, organoboron compounds, ionizing ionic compounds, or anycombination thereof.

2. Chemically-Treated Solid Oxide Activator-Supports

a. Overview

The present techniques encompass catalyst compositions that include anacidic activator-support, such as, for example, a chemically-treatedsolid oxide (CTSO). A CTSO may be used in combination with anorganoaluminum compound. The activator-support may include a solid oxidetreated with an electron-withdrawing anion. The solid oxide may includesuch compounds as silica, alumina, silica-alumina, aluminophosphate,aluminum phosphate, zinc aluminate, heteropolytungstates, titania,zirconia, magnesia, boria, zinc oxide, mixed oxides thereof, and thelike, or any mixture or combination thereof. The electron-withdrawinganion may include fluoride, chloride, bromide, iodide, phosphate,triflate, bisulfate, sulfate, sulfite, fluoroborate, fluorosulfate,trifluoroacetate, phosphate, fluorophosphate, fluorozirconate,fluorosilicate, fluorotitanate, permanganate, substituted orunsubstituted alkanesulfonate, substituted or unsubstitutedarenesulfonate, substituted or unsubstituted alkylsulfate, or anycombination thereof.

The activator-support may include the contact product of a solid oxidecompound and an electron-withdrawing anion source, as presented in thefollowing subsection b. The solid oxide compound may include aninorganic oxide and may be optionally calcined prior to contacting theelectron-withdrawing anion source. The contact product may also becalcined either during or after the solid oxide compound is contactedwith the electron-withdrawing anion source. In this embodiment, thesolid oxide compound may be calcined or uncalcined. In anotherembodiment, the activator-support may include the contact product of acalcined solid oxide compound and an electron-withdrawing anion source.

The treated activator-support may exhibit enhanced activity as comparedto the corresponding untreated solid oxide compound. While not intendingto be bound by theory, it is believed that the activator-support canfunction as a solid oxide supporting compound with an additionalionizing, polarizing, or bond weakening function, collectively termed an“activating” function, by weakening the metal-ligand bond between ananionic ligand and the metal in the metallocene. Thus, theactivator-support may be considered to exhibit an “activating” function,regardless of whether it ionizes the metallocene, abstracts an anionicligand to form an ion pair, weakens the metal-ligand bond in themetallocene, simply coordinates to an anionic ligand when it contactsthe activator-support, or any other mechanisms by which ionizing,polarizing, or bond weakening might occur. In preparing themetallocene-based catalyst compositions of the present techniques, theactivator-support is typically used along with a component that providesan activatable ligand such as an alkyl or hydride ligand to themetallocene, including but not limited to an organoaluminum compound,when the metallocene compound does not already include such a ligand. Inone embodiment the treated solid oxide may be contacted with thealuminum alkyl before being exposed to the metallocene.

The activator-support may include a solid inorganic oxide material, amixed oxide material, or a combination of inorganic oxide materials thatis chemically-treated with an electron-withdrawing component, andoptionally treated with another metal ion. Thus, the solid oxide of thepresent techniques encompasses oxide materials such as alumina, “mixedoxide” compounds such as silica-alumina or silica-zirconia orsilica-titania, and combinations and mixtures thereof. The mixed metaloxide compounds such as silica-alumina, with more than one metalcombined with oxygen to form a solid oxide compound, may be made byco-gellation, impregnation or chemical deposition, and are encompassedby the present techniques.

Further, the activator-support may include an additional metal or metalion such as zinc, nickel, vanadium, silver, copper, gallium, tin,tungsten, molybdenum, or any combination thereof. Examples ofactivator-supports that further include an additional metal or metal ioninclude, for example, chlorided zinc-impregnated alumina, fluoridedzinc-impregnated alumina, chlorided vanadium-impregnated alumina,fluorided zinc-impregnated silica-alumina, chlorided nickel-impregnatedalumina, or any combination thereof.

The activator-support of the present techniques may include a solidoxide of relatively high porosity, which exhibits Lewis acidic orBrønsted acidic behavior. The solid oxide may be chemically-treated withan electron-withdrawing component, typically an electron-withdrawinganion, to form an activator-support. While not intending to be bound bytheory, it is believed that treatment of the inorganic oxide with anelectron-withdrawing component augments or enhances the acidity of theoxide. Thus, the activator-support exhibits Lewis or Brønsted aciditywhich is typically greater than the Lewis or Brønsted acidity of theuntreated solid oxide. The polymerization activity of thechemically-treated solid oxide may be enhanced over the activity shownby an untreated solid oxide.

The chemically-treated solid oxide may include a solid inorganic oxide,including oxygen and an element selected from Group 2, 3, 4, 5, 6, 7, 8,9, 10, 11, 12, 13, 14, or 15 of the periodic table, or including oxygenand an element selected from the lanthanide or actinide elements. Forexample, the inorganic oxide may include oxygen and an element selectedfrom Al, B, Be, Bi, Cd, Co, Cr, Cu, Fe, Ga, La, Mn, Mo, Ni, Sb, Si, Sn,Sr, Th, Ti, V, W, P, Y, Zn or Zr.

Suitable solid oxide materials or compounds that may be used in thechemically-treated solid oxide of the present techniques may include,for example, Al₂O₃, B₂O₃, BeO, Bi₂O₃, CdO, Co₃O₄, Cr₂O₃, CuO, Fe₂O₃,Ga₂O₃, La₂O₃, Mn₂O₃, MoO₃, NiO, P₂O₅, Sb₂O₅, SiO₂, SnO₂, SrO, ThO₂,TiO₂, V₂O₅, WO₃, Y₂O₃, ZnO, ZrO₂, and the like, including mixed oxidesthereof, and combinations thereof. Mixed oxides that may be used in theactivator-support of the present techniques may include, for example,mixed oxides of any combination of Al, B, Be, Bi, Cd, Co, Cr, Cu, Fe,Ga, La, Mn, Mo, Ni, P, Sb, Si, Sn, Sr, Th, Ti, V, W, Y, Zn, Zr, and thelike. Examples of mixed oxides that may be used in the activator-supportof the present techniques may also include silica-alumina,silica-titania, silica-zirconia, zeolites, many clay minerals, pillaredclays, alumina-titania, alumina-zirconia, aluminophosphate, and thelike. Procedures to form such solid oxides, and exemplary chemicallytreated solid oxides are presented in the following subsections c and d,respectively. Concentrations of electron-withdrawing anions that may beuseful in forming chemically treated solid oxides are presented in thefollowing subsection e.

b. Chemical Treatment of the Solid Oxide

A solid oxide material that may be used in the present techniques may bechemically-treated by contacting it with an electron-withdrawingcomponent, typically an electron-withdrawing anion source, to cause orenhance activation of the metallocene complex. Further, the solid oxidematerial may be chemically-treated with another metal ion, that may bethe same as or different from any metal element that constitutes thesolid oxide material, then calcined to form a metal-containing ormetal-impregnated chemically-treated solid oxide. Alternatively, a solidoxide material and an electron-withdrawing anion source may be contactedand calcined simultaneously. The method by which the oxide may becontacted with an electron-withdrawing component, typically a salt or anacid of an electron-withdrawing anion, may include, for example,gelling, co-gelling, impregnation of one compound onto another,vaporization of one compound onto the other, and the like. Inembodiments of the present techniques, following any contacting method,the contacted mixture of oxide compound, electron-withdrawing anion, andoptionally the metal ion may be calcined.

The electron-withdrawing component used to treat the oxide may be anycomponent that increases the Lewis or Brønsted acidity of the solidoxide upon treatment. In one embodiment, the electron-withdrawingcomponent is typically an electron-withdrawing anion derived from asalt, an acid, or other compound such as a volatile organic compoundthat can serve as a source or precursor for that anion. Examples ofelectron-withdrawing anions include, for example, fluoride, chloride,bromide, iodide, phosphate, trifluoromethane sulfonate (triflate),bisulfate, sulfate, fluoroborate, fluorosulfate, trifluoroacetate,phosphate, fluorophosphate, fluorozirconate, fluorosilicate,fluorotitanate, permanganate, substituted or unsubstitutedalkanesulfonate, substituted or unsubstituted arenesulfonate,substituted or unsubstituted alkylsulfate, and the like, including anymixtures and combinations thereof. In addition, other ionic or non-ioniccompounds that serve as sources for these electron-withdrawing anionsmay also be used in the present techniques. The chemically-treated solidoxide may include a sulfated solid oxide or a sulfated alumina.

The terms alkanesulfonate and alkyl sulfate refer to anions having thegeneral formula [R^(B)SO₂O]⁻ and [(R^(B)O)SO₂O]⁻, respectively, whereinR^(B) may be a linear or branched alkyl group having up to 20 carbonatoms, that may be substituted with a group selected independently fromF, Cl, Br, I, OH, OMe, OEt, OCF₃, Ph, xylyl, mesityl, or OPh. Thus, thealkanesulfonate and alkyl sulfate may be referred to as being eithersubstituted or unsubstituted. In one embodiment, the alkyl group of thealkanesulfonate or alkyl sulfate may have up to 12 carbon atoms. Inanother embodiment, the alkyl group of the alkanesulfonate or alkylsulfate may have up to 8 carbon atoms, or up to 6 carbon atoms. Suchalkanesulfonates may include, for example, methanesulfonate,ethanesulfonate, 1-propanesulfonate, 2-propanesulfonate,3-methylbutanesulfonate, trifluoromethanesulfonate,trichloromethanesulfonate, chloromethanesulfonate,1-hydroxyethanesulfonate, 2-hydroxy-2-propanesulfonate,1-methoxy-2-propanesulfonate, and the like. In other embodiments,examples of alkyl sulfates include, for example, methylsulfate,ethylsulfate, 1-propylsulfate, 2-propylsulfate, 3-methylbutylsulfate,trifluoromethanesulfate, trichloromethylsulfate, chloromethylsulfate,1-hydroxyethylsulfate, 2-hydroxy-2-propylsulfate,1-methoxy-2-propylsulfate, and the like.

The term arenesulfonate refers to anions having the general formula[Ar^(A)SO₂O]⁻, wherein Ar^(A) may be an aryl group having up to 14carbon atoms, and which may be optionally substituted with a groupselected independently from F, Cl, Br, I, Me, Et, Pr, Bu, OH, OMe, OEt,OPr, OBu, OCF₃, Ph, OPh, or R^(C), wherein R^(C) may be a linear orbranched alkyl group having up to 20 carbon atoms. Thus, thearenesulfonate may be referred to as a substituted or an unsubstitutedarenesulfonate. Because the aryl group Ar^(A) may be substituted with analkyl side chain, R^(C), which may include a long alkyl side chain, theterm arenesulfonate encompasses detergents. The aryl group of thearenesulfonate may have up to 10 carbon atoms, or up to 6 carbon atoms.Examples of such arenesulfonates include, for example, benzenesulfonate,naphthalenesulfonate, p-toluenesulfonate, m-toluenesulfonate,3,5-xylenesulfonate, trifluoromethoxybenzenesulfonate,trichloromethoxybenzenesulfonate, trifluoromethyl-benzenesulfonate,trichloromethylbenzenesulfonate, fluorobenzenesulfonate,chlorobenzenesulfonate, 1-hydroxyethanebenzenesulfonate,3-fluoro-4-methoxybenzenesulfonate, and the like.

When the electron-withdrawing component includes a salt of anelectron-withdrawing anion, the counterion or cation of that salt may beany cation that allows the salt to revert or decompose back to the acidduring calcining. Factors that dictate the suitability of the particularsalt to serve as a source for the electron-withdrawing anion mayinclude, for example, the solubility of the salt in the desired solvent,the lack of adverse reactivity of the cation, ion-pairing effectsbetween the cation and anion, hygroscopic properties imparted to thesalt by the cation, and the like, and thermal stability of the anion.Examples of suitable cations in the salt of the electron-withdrawinganion include, for example, ammonium, trialkyl ammonium, tetraalkylammonium, tetraalkyl phosphonium, H⁺, [H(OEt₂)₂]⁺, and the like.

c. Examples of Processes to Produce a Chemically Treated Solid Oxide

Combinations of one or more different electron withdrawing anions, invarying proportions, may be used to tailor the specific acidity of theactivator-support to the desired level. Such combinations may becontacted with the oxide material simultaneously or individually, and inany order that affords the desired activator-support acidity. Forexample, the present techniques may employ two or moreelectron-withdrawing anion source compounds in two or more separatecontacting steps. Thus, one example of such a process by which anactivator-support may be prepared is as follows. A selected solid oxidecompound, or combination of oxide compounds, is contacted with a firstelectron-withdrawing anion source compound to form a first mixture andthis first mixture is calcined. The calcined first mixture is contactedwith a second electron-withdrawing anion source compound to form asecond mixture. The second mixture is calcined to form a treated solidoxide compound. In such a process, the first and secondelectron-withdrawing anion source compounds may be different compoundsor they may be the same compound.

The solid oxide activator-support may be produced by a process thatincludes contacting a solid oxide compound with an electron-withdrawinganion source compound to form a first mixture. The first mixture is thencalcined to form the solid oxide activator-support.

In other embodiments, the solid oxide activator-support may be producedby a process that includes contacting a solid oxide compound with afirst electron-withdrawing anion source compound to form a firstmixture. The first mixture is calcined, and then the calcined firstmixture is contacted with a second electron-withdrawing anion sourcecompound to form a second mixture. The second mixture is calcined toform the solid oxide activator-support. The solid oxideactivator-support may be referred to as a chemically treated solid oxide(CTSO) compound.

Alternatively, the solid oxide activator-support may be produced bycontacting a solid oxide with an electron-withdrawing anion sourcecompound. In this procedure the solid oxide compound may be calcinedbefore, during or after contacting with the electron-withdrawing anionsource, and when there are aluminoxanes or organoborates present.

Calcining of the treated solid oxides may be conducted in an ambient orinert atmosphere, typically in a dry ambient atmosphere, at atemperature from about 200° C. to about 900° C., and for a time of about1 minute to about 100 hours. In other embodiments, calcining may beconducted at a temperature from about 300° C. to about 800° C. and inyet other embodiments, calcining may be conducted at a temperature fromabout 400° C. to about 700° C. Calcining may be conducted from about 1hour to about 50 hours, or from about 3 hours to about 20 hours. Inexemplary embodiments, calcining may be carried out from about 1 toabout 10 hours at a temperature from about 350° C. to about 550° C.

Further, calcining may typically be conducted in an ambient atmosphere,at the elevated temperature. Generally, calcining may be conducted in anoxidizing atmosphere, such as air. Alternatively, calcining may beperformed in an inert atmosphere, such as nitrogen or argon, or in areducing atmosphere such as hydrogen or carbon monoxide.

The solid oxide component used to prepare the chemically-treated solidoxide may have a pore volume greater than about 0.1 cc/g, a pore volumegreater than about 0.5 cc/g, or a pore volume greater than about 1.0cc/g. The solid oxide component may have a surface area from about 100to about 1000 m²/g, from about 200 to about 800 m²/g, or from about 250to about 600 m²/g.

d. Examples of Chemically Treated Solid Oxides

The solid oxide material may be treated with a source of halide ion orsulfate ion, or a combination of anions, and optionally treated with ametal ion, then calcined to provide the activator-support in the form ofa particulate solid. For example, the solid oxide material may betreated with a source of sulfate, termed a sulfating agent, a source ofchloride ion, termed a chloriding agent, a source of fluoride ion,termed a fluoriding agent, or a combination thereof, and calcined toprovide the solid oxide activator. Examples of useful acidicactivator-supports may include, for example: bromided alumina; chloridedalumina; fluorided alumina; sulfated alumina; bromided silica-alumina,chlorided silica-alumina; fluorided silica-alumina; sulfatedsilica-alumina; bromided silica-zirconia; chlorided silica-zirconia;fluorided silica-zirconia; sulfated silica-zirconia; chloridedzinc-alumina; triflate treated silica-alumina; fluorided silica-titania,silica treated with fluoroborate, a pillared clay, such as a pillaredmontmorillonite, optionally treated with fluoride, chloride, or sulfate;phosphated alumina, or other aluminophosphates, optionally treated withsulfate, fluoride, or chloride; or any combination thereof. Further, anyof the activator-supports may optionally be treated with another metalion, typically from a metal salt or compound, wherein the metal ion maybe the same as or different from any metal that makes up the solid oxidematerial.

The treated oxide activator-support may include a fluorided solid oxidein the form of a particulate solid, thus a source of fluoride ion may beadded to the oxide by treatment with a fluoriding agent. For example,fluoride ion may be added to the oxide by forming a slurry of the oxidein a suitable solvent such as alcohol or water, including, for example,alcohols having one to three carbon alcohols. Such alcohols may beselected due to their volatility and low surface tension. Alternatively,the fluoriding source may be dry-mixed with the solid oxide prior tocalcining. Examples of fluoriding agents that may be used in the presenttechniques include hydrofluoric acid (HF), ammonium fluoride (NH₄F),ammonium bifluoride (NH₄HF₂), ammonium tetrafluoroborate (NH₄BF₄),ammonium silicofluoride (hexafluorosilicate) ((NH₄)₂SiF₆), ammoniumhexafluorophosphate (NH₄PF₆), tetrafluoroboric acid (HBF₄), ammoniumhexafluorotitanate (NH₄)₂TiF₆, ammonium hexafluorozirconate (NH₄)₂ZrF₆,analogs thereof, and combinations thereof. A specific fluoriding agent,ammonium bifluoride NH₄HF₂, is often used due to its ease of use andready availability.

The solid oxide may be treated with a fluoriding agent during thecalcining step. Any fluoriding agent capable of thoroughly contactingthe solid oxide during the calcining step may be used. For example, inaddition to those fluoriding agents described previously, volatileorganic fluoriding agents may be used. Such volatile organic fluoridingagents that may be used in embodiments include, for example, freons,perfluorohexane, perfluorobenzene, fluoromethane, trifluoroethanol, andcombinations thereof. Gaseous hydrogen fluoride or fluorine itself mayalso be used with the solid oxide is fluorided during calcining. Oneconvenient method of contacting the solid oxide with the fluoridingagent may be to vaporize a fluoriding agent into a gas stream used tofluidize the solid oxide during calcination.

Similarly, the chemically-treated solid oxide may include a chloridedsolid oxide in the form of a particulate solid, thus a source ofchloride ion may be added to the oxide by treatment with a chloridingagent. The chloride ion may be added to the oxide by forming a slurry ofthe oxide in a suitable solvent. The solid oxide may also be treatedwith a chloriding agent during the calcining step. Any chloriding agentthat may be capable of serving as a source of chloride and thoroughlycontacting the oxide during the calcining step may be used. For example,volatile organic chloriding agents may be used. Examples of suchvolatile organic chloriding agents include, for example, certain freons,perchlorobenzene, chloromethane, dichloromethane, chloroform, carbontetrachloride, trichloroethanol, or volatile metal chlorides like SiCl₄,AlCl₃, TiCl₄, ZrCl₄, BCl₃, SnCl₄, etc. or any combination thereof.Gaseous hydrogen chloride or chlorine itself may also be used with thesolid oxide during calcining. One convenient method of contacting theoxide with the chloriding agent may be to vaporize a chloriding agentinto a gas stream used to fluidize the solid oxide during calcination.

e. Concentration of Electron-Withdrawing Anions

When the activator-support includes a chemically-treated solid oxideincluding a solid oxide treated with an electron-withdrawing anion, theelectron withdrawing anion may be added to the solid oxide in an amountgreater than about 1% by weight of the solid oxide. The electronwithdrawing anion may be added to the solid oxide in an amount greaterthan about 2% by weight of the solid oxide, greater than about 3% byweight of the solid oxide, greater than about 5% by weight of the solidoxide, or greater than about 7% by weight of the solid oxide.

The amount of electron-withdrawing ion, for example fluoride or chlorideion, present before calcining the solid oxide may be from about 1 toabout 50% by weight, where the weight percents are based on the weightof the solid oxide, for example silica-alumina, before calcining. Theamount of electron-withdrawing ion, for example fluoride or chlorideion, present before calcining the solid oxide may be from about 3 toabout 25% by weight or from about 4 to about 20% by weight.Alternatively, halide ion or may be used in an amount sufficient todeposit, after calcining, from about 0.1% to about 50%, from about 0.5%to about 40%, or from about 1% to about 30% by weight halide ionrelative to the weight of the solid oxide. If the fluoride or chlorideion is added during calcining, such as when calcined in the presence ofCCl₄, there may be typically no, or only trace levels, of fluoride orchloride ion in the solid oxide before calcining Once impregnated withhalide, the halided oxide may be dried by any method. Such methods mayinclude, for example, suction filtration followed by evaporation, dryingunder vacuum, spray drying, and the like. It may also be possible toinitiate the calcining step immediately without drying the impregnatedsolid oxide.

The silica-alumina used to prepare the treated silica-alumina may have apore volume greater than about 0.5 cc/g. Alternatively, the pore volumemay be greater than about 0.8 cc/g, or greater than about 1.0 cc/g.Further, the silica-alumina may have a surface area greater than about100 m²/g, 250 m²/g, or 350 m²/g. Generally, the silica-alumina of thepresent techniques may have an alumina content from about 5 to about95%. Alternatively, the alumina content of the silica-alumina may befrom about 5 to about 50%, or from about 8% to about 30% alumina byweight.

The sulfated solid oxide may include sulfate and a solid oxide componentsuch as alumina or silica-alumina, in the form of a particulate solid.Optionally, the sulfated oxide may be further treated with a metal ionsuch that the calcined sulfated oxide may include a metal. For example,the sulfated solid oxide may include sulfate and alumina. The sulfatedalumina may be formed by a process wherein the alumina is treated with asulfate source, including, for example, sulfuric acid or a sulfate saltsuch as ammonium sulfate, zinc sulfate, aluminum sulfate, nickel sulfateor copper sulfate, among others. In embodiments, this process may beperformed by forming a slurry of the alumina in a suitable solvent suchas alcohol or water, in which the desired concentration of the sulfatingagent has been added. Suitable organic solvents include, for example,the one to three carbon alcohols because of their volatility and lowsurface tension. Alternatively the sulfate salt, such as ammoniumbisulfate, can be dry mixed with the alumina before calcining.

The amount of sulfate ion present before calcining may be from about 1%to about 50% by weight, from about 2% to about 30% by weight, or fromabout 5% to about 25% by weight, where the weight percents are based onthe weight of the solid oxide before calcining. Once impregnated withsulfate, the sulfated oxide may be dried by any method including, butnot limited to, suction filtration followed by evaporation, drying undervacuum, spray drying, and the like, although it may also be possible toinitiate the calcining step immediately.

In addition to being treated with an electron-withdrawing component suchas halide or sulfate ion, the solid inorganic oxide of the presenttechniques may be treated with a metal source, including metal salts ormetal-containing compounds. These compounds may be added to orimpregnated onto the solid oxide in solution form, and subsequentlyconverted into the supported metal upon calcining. Accordingly, thesolid inorganic oxide may further include zinc, nickel, vanadium,silver, copper, gallium, tin, tungsten, molybdenum, or a combinationthereof. For example, zinc may be used to impregnate the solid oxidebecause it provides good catalyst activity and low cost. The solid oxidemay be treated with metal salts or metal-containing compounds before,after, or at the same time that the solid oxide may be treated with theelectron-withdrawing anion.

Further, any method of impregnating the solid oxide material with ametal may be used. The method by which the oxide is contacted with ametal source, typically a salt or metal-containing compound, mayinclude, for example, gelling, co-gelling, impregnation of one compoundonto the other, and similar techniques. Following any contacting method,the contacted mixture of oxide compound, electron-withdrawing anion, andthe metal ion may be calcined. Alternatively, a solid oxide material, anelectron-withdrawing anion source, and the metal salt ormetal-containing compound may be contacted and calcined simultaneously.

The ansa-metallocene compound may be contacted with an olefin monomerand an organoaluminum cocatalyst for a first period of time prior tocontacting this mixture with an acidic activator-support. Once theprecontacted mixture of metallocene, monomer, and a component thatprovides an activatable ligand to the metallocene, e.g., anorganoaluminum cocatalyst, is contacted with the acidicactivator-support, the composition may be termed the “postcontacted”mixture. The postcontacted mixture may be allowed to remain in furthercontact for a second period of time prior to being charged into thereactor in which the polymerization process will be carried out.

Various processes to prepare solid oxide activator-supports that may beused in the present techniques have been reported. For example, U.S.Pat. Nos. 6,107,230, 6,165,929, 6,294,494, 6,300,271, 6,316,553,6,355,594, 6,376,415, 6,391,816, 6,395,666, 6,524,987, and 6,548,441,describe such methods, each of which is incorporated by reference in itsentirety herein.

3. Ion-Exchangeable and Layered Mineral Activator-Supports

The activator-support of the present techniques may include clayminerals having exchangeable cations and layers capable of expanding.These activator supports include ion-exchangeable materials, such as,for example, silicate and aluminosilicate compounds or minerals, eitherwith layered or non-layered structures, and any combination thereof.Typical clay mineral activator-supports include layered aluminosilicatessuch as pillared clays. Although the term “support” may be used, it isnot meant to be construed as an inert component of the catalystcomposition, but rather may be considered an active part of the catalystcomposition, because of its intimate association with theansa-metallocene and the component that provides an activatable ligandto the metallocene, such as an organoaluminum. While not intending to bebound by theory, it is believed that the ion exchangeableactivator-support may serve as an insoluble reactant that reacts withthe ansa-metallocene and organoaluminum components to form a catalystcomposition used to produce polymer. When the acidic activator-supportincludes an ion-exchangeable activator-support, it may optionally betreated with an electron-withdrawing anion such as those discussedabove, though typically the ion-exchangeable activator-support is nottreated with an electron-withdrawing anion.

The clay materials of the present techniques may encompass materialseither in their natural state or that have been treated with variousions by wetting, ion exchange, or pillaring. The clay materialactivator-support of the present techniques may include clays that havebeen ion exchanged with large cations, including polynuclear, highlycharged metal complex cations. However, the clay materialactivator-supports of the present techniques also encompass clays thathave been ion exchanged with simple salts, including, but not limitedto, salts of Al(III), Fe(II), Fe(III) and Zn(II) with ligands such ashalide, acetate, sulfate, nitrate, or nitrite.

The clay activator-support of the present techniques may includepillared clays. The term pillared clays may be used to refer to claymaterials that have been ion exchanged with large, typicallypolynuclear, highly charged metal complex cations. Examples of such ionsinclude, for example, Keggin ions which may have charges such as 7+,various polyoxometallates, and other large ions. Thus, the termpillaring refers to a simple exchange reaction in which the exchangeablecations of a clay material may be replaced with large, highly chargedions, such as Keggin ions. These polymeric cations may then beimmobilized within the interlayers of the clay and when calcined areconverted to metal oxide “pillars,” effectively supporting the claylayers as column-like structures. Thus, once the clay is dried andcalcined to produce the supporting pillars between clay layers, theexpanded lattice structure may be maintained, enhancing the porosity.The resulting pores can vary in shape and size as a function of thepillaring material and the parent clay material used.

The pillaring process utilizes clay minerals having exchangeable cationsand layers capable of expanding. Any pillared clay that can enhance thepolymerization of olefins in the catalyst composition of the presenttechniques may be used. Therefore, suitable clay minerals for pillaringmay include, for example: allophanes; smectites, including dioctahedral(Al) and tri-octahedral (Mg) smectites and derivatives thereof, such as,montmorillonites (bentonites), nontronites, hectorites, or laponites;halloysites; vermiculites; micas; fluoromicas; chlorites; mixed-layerclays; the fibrous clays such as sepiolites and attapulgites(palygorskites); serpentine clays; illite; laponite; saponite; or anycombination thereof. In one embodiment, the pillared clayactivator-support may include bentonite or montmorillonite, noting thatthe principal component of bentonite is montmorillonite.

The ion-exchangeable activator-supports such as pillared clays used toprepare the catalyst compositions of the present techniques may becombined with other inorganic support materials, including, for example,zeolites, inorganic oxides, phosphated inorganic oxides, and the like.In embodiments, typical support materials that may be used in thisregard include, for example, silica, silica-alumina, alumina, titania,zirconia, magnesia, boria, fluorided alumina, silated alumina, thoria,aluminophosphate, aluminum phosphate, zinc aluminate, phosphated silica,phosphated alumina, silica-titania, coprecipitated silica/titania,fluorided/silated alumina, and any combination or mixture thereof. Theamount of ansa-metallocene compound in relation to the ion-exchangeableactivator-support used to prepare the catalyst composition of thepresent techniques may be from about 0.1 wt % to about 15 wt %ansa-metallocene complex, based on the weight of the activator-supportcomponent (not based on the final metallocene-clay mixture), or fromabout 1 wt % to about 10 wt % ansa-metallocene.

The mixture of ansa-metallocene and clay activator-support may becontacted and mixed for any length of time sufficient to allow thoroughinteraction between the ansa-metallocene and activator-support.Sufficient deposition of the metallocene component on the clay may beachieved without heating a mixture of clay and metallocene complex. Forexample, the ansa-metallocene compound and the clay material may besimply mixed at a temperature range from about room temperature to about200° F. in order to achieve the deposition of the ansa-metallocene onthe clay activator-support. Alternatively, the ansa-metallocene compoundand the clay material may be mixed from about 100° F. to about 180° F.in order to achieve the deposition of the ansa-metallocene on the clayactivator-support.

The present techniques encompass catalyst compositions including anacidic activator-support, which may include a layered mineral. The term“layered mineral” is used herein to describe materials such as clayminerals, pillared clays, ion-exchanged clays, exfoliated clays,exfoliated clays gelled into another oxide matrix, layered mineralsmixed or diluted with other materials, and the like, or any combinationthereof. When the acidic activator-support includes a layered mineral,it may optionally be treated with an electron-withdrawing anion such asthose presented herein, though typically the layered mineral is nottreated with an electron-withdrawing anion. For example, a clay mineralmay be used as the activator-support.

Clay minerals generally include the large group of finely-crystalline,sheet-like layered minerals that are found in nature in fine-grainedsediments, sedimentary rocks, and the like, and which constitute a classof hydrous silicate and aluminosilicate minerals with sheet-likestructures and very high surface areas. This term may also be used todescribe hydrous magnesium silicates with a phyllosilicate structure.Examples of clay minerals that may be used in the present techniquesinclude, for example, allophanes; smectites, including dioctahedral (Al)and tri-octahedral (Mg) smectites and derivatives thereof such asmontmorillonites (bentonites), nontronites, hectorites, or laponites;halloysites; vermiculites; micas; fluoromicas; chlorites; mixed-layerclays; the fibrous clays, such as sepiolites and attapulgites(palygorskites); a serpentine clay; illite; laponite; saponite; or anycombination thereof. Many common clay minerals belong to the kaolinite,montmorillonite, or illite groups of clays.

When layered minerals are used as activator-supports or metalloceneactivators, the layered minerals may be calcined prior to their use asactivators. Typical calcination temperatures may range from about 100°C. to about 700° C., from about 150° C. to about 500° C., or from about200° C. to about 400° C.

4. Organoaluminoxane Activators/Cocatalysts

The present techniques may include catalyst compositions that useorganoaluminoxane compounds as activators and/or cocatalysts. In theseembodiments, the catalyst composition may not require an acidicactivator-support such as a chemically-treated solid oxide to weaken thebonds between the metal and the X³ or X⁴ ligands, as theorganoaluminoxane may perform this function, or may replace the X³ or X⁴ligands with more active species. The catalyst composition may also notrequire an organoaluminum compound. Thus, any ansa-metallocene compoundspresented herein may be combined with any of the aluminoxanes presentedherein, or any combination of aluminoxanes presented herein, to formcatalyst compositions of the present techniques. Further, anyansa-metallocene compounds presented herein may be combined with anyaluminoxane or combination of aluminoxanes, and optionally anactivator-support such as, for example, a layered mineral, anion-exchangeable activator-support, an organoboron compound or anorganoborate compound, to form a catalyst composition of the presenttechniques.

Aluminoxanes may be referred to as poly(hydrocarbyl aluminum oxides) ororganoaluminoxanes. The other catalyst components may be contacted withthe aluminoxane in a saturated hydrocarbon compound solvent, though anysolvent which may be substantially inert to the reactants,intermediates, and products of the activation step may be used. Thecatalyst composition formed in this manner may be collected by anymethods, including but not limited to filtration, or the catalystcomposition may be introduced into the polymerization reactor withoutbeing isolated.

The aluminoxane compound of the present techniques may be an oligomericaluminum compound, wherein the aluminoxane compound may include linearstructures, cyclic, or cage structures, or mixtures of all three. Cyclicaluminoxane compounds having the formula:

whereinR may be a linear or branched alkyl having from 1 to 10 carbon atoms,and n may be an integer from 3 to about 10 may be encompassed by thepresent techniques. The (AlRO)_(n) moiety shown here also constitutesthe repeating unit in a linear aluminoxane. Thus, linear aluminoxaneshaving the formula:

whereinR may be a linear or branched alkyl having from 1 to 10 carbon atoms,and n may be an integer from 1 to about 50, are also encompassed by thepresent techniques.

Further, aluminoxanes may also have cage structures of the formula R^(t)_(5m+α)R^(b) _(m-α)Al_(4m)O_(3m), wherein m may be 3 or 4 and α is equalto n_(Al(3))−n_(O(2))+n_(O(4)). In this structure n_(Al(3)) is thenumber of three coordinate aluminum atoms, n_(O(2)) is the number of twocoordinate oxygen atoms, and n_(O(4)) is the number of 4 coordinateoxygen atoms. R^(t) represents a terminal alkyl group and R^(b)represents a bridging alkyl group, either of which may have from 1 to 10carbon atoms.

Thus, aluminoxanes may be represented generally by formulas such as(R—Al—O)_(n), R(R—Al—O)_(n)AlR₂, and the like, wherein the R group maybe a linear or branched C₁-C₆ alkyl such as methyl, ethyl, propyl,butyl, pentyl, or hexyl, and n may represent an integer from 1 to about50. The aluminoxane compounds of the present techniques may include, forexample, methylaluminoxane, ethylaluminoxane, n-propylaluminoxane,iso-propylaluminoxane, n-butylaluminoxane, t-butylaluminoxane,sec-butylaluminoxane, iso-butylaluminoxane, 1-pentylaluminoxane,2-pentylaluminoxane, 3-pentylaluminoxane, iso-pentylaluminoxane,neopentylaluminoxane, or combinations thereof.

While organoaluminoxanes with different types of R groups areencompassed by the present techniques, methyl aluminoxane (MAO), ethylaluminoxane, or isobutyl aluminoxane may also be used as cocatalystsused in the compositions of the present techniques. These aluminoxanesmay be prepared from trimethylaluminum, triethylaluminum, ortriisobutylaluminum, respectively, and may be referred to as poly(methylaluminum oxide), poly(ethyl aluminum oxide), and poly(isobutyl aluminumoxide), respectively. It is also within the scope of the currenttechniques to use an aluminoxane in combination with a trialkylaluminum,such as disclosed in U.S. Pat. No. 4,794,096, which is hereinincorporated by reference in its entirety.

The present techniques encompass many values of n in the aluminoxaneformulas (R—Al—O)_(n) and R(R—Al—O)_(n)AlR₂. In typical aluminoxanes, nis at least about 3. However, depending upon how the organoaluminoxaneis prepared, stored, and used, the value of n may be variable within asingle sample of aluminoxane, and such combinations oforganoaluminoxanes are encompassed by the methods and compositions ofthe present techniques.

In embodiments of the present techniques that include the optionalaluminoxane, the molar ratio of the aluminum in the aluminoxane to themetallocene in the composition may be from about 1:10 to about100,000:1, or from about 5:1 to about 15,000:1. The amount of optionalaluminoxane added to a polymerization zone may be an amount within arange of about 0.01 mg/L to about 1000 mg/L, from about 0.1 mg/L toabout 100 mg/L, or from about 1 mg/L to about 50 mg/L.

Organoaluminoxanes may be prepared by various procedures which areavailable. Examples of organoaluminoxane preparations are disclosed inU.S. Pat. Nos. 3,242,099 and 4,808,561, each of which is incorporated byreference in its entirety herein. One example of how an aluminoxane maybe prepared is as follows. Water may be dissolved in an inert organicsolvent and then reacted with an aluminum alkyl compound such as AlR₃ toform the desired organoaluminoxane compound. While not intending to bebound by this statement, it is believed that this synthetic method canafford a mixture of both linear and cyclic (R—Al—O)_(n) aluminoxanespecies, both of which are encompassed by the present techniques.Alternatively, organoaluminoxanes may be prepared by reacting analuminum alkyl compound such as AlR₃ with a hydrated salt, such ashydrated copper sulfate, in an inert organic solvent.

5. Organoboron and Organoborate Activators/Cocatalysts

The present techniques may also include catalyst compositions that useorganoboron or organoborate compounds as activators and/or cocatalysts.Any ansa-metallocene compound presented herein may be combined with anyof the organoboron or organoborate cocatalysts presented herein, or anycombination of organoboron or organoborate cocatalysts presented herein.This composition may include a component that provides an activatableligand such as an alkyl or hydride ligand to the metallocene, when themetallocene compound does not already include such a ligand, such as anorganoaluminum compound. Further, any ansa-metallocene compoundspresented herein may be combined with: any an organoboron ororganoborate cocatalyst; an organoaluminum compound; optionally, analuminoxane; and optionally, an activator-support; to form a catalystcomposition of the present techniques.

The term “organoboron” compound may be used to refer to neutral boroncompounds, borate salts, or combinations thereof. For example, theorganoboron compounds in various embodiments may be a fluoroorgano boroncompound, a fluoroorgano borate compound, or a combination thereof. Anyfluoroorgano boron or fluoroorgano borate compound may be utilized. Theterm fluoroorgano boron has its usual meaning to refer to neutralcompounds of the form BY₃. The term fluoroorgano borate compound alsohas its usual meaning to refer to the monoanionic salts of afluoroorgano boron compound of the form [cation]⁺[BY₄]⁻, where Yrepresents a fluorinated organic group. For convenience, fluoroorganoboron and fluoroorgano borate compounds may be referred to collectivelyby organoboron compounds, or by either name as the context requires.

Fluoroorgano borate compounds that may be used as cocatalysts in thepresent techniques include, for example, fluorinated aryl borates suchas, N,N-dimethylanilinium tetrakis(pentafluorophenyl)borate,triphenylcarbenium tetrakis(pentafluorophenyl)borate, lithiumtetrakis(pentafluorophenyl)borate, N,N-dimethylaniliniumtetrakis[3,5-bis(trifluoromethyl)phenyl]borate, triphenylcarbeniumtetrakis[3,5-bis(trifluoromethyl)phenyl]borate, and the like, includingmixtures thereof. Examples of fluoroorgano boron compounds that may beused as cocatalysts in the present techniques include, for example,tris(pentafluorophenyl)boron, tris[3,5-bis(trifluoromethyl)phenyl]boron,and the like, including mixtures thereof.

Although not intending to be bound by the following theory, theseexamples of fluoroorgano borate and fluoroorgano boron compounds, andrelated compounds, are thought to form weakly-coordinating anions whencombined with organometal compounds, as disclosed in U.S. Pat. No.5,919,983, which is herein included by reference in its entirety herein.

Generally, any amount of organoboron compound may be utilized in thepresent techniques. In some embodiments, the molar ratio of theorganoboron compound to the metallocene compound in the composition maybe from about 0.1:1 to about 10:1, or from about 0.5 mole to about 10moles of boron compound per mole of metallocene compound. Inembodiments, the amount of fluoroorgano boron or fluoroorgano boratecompound used as a cocatalyst for the metallocene may range of fromabout 0.8 mole to about 5 moles of boron compound per mole ofmetallocene compound.

6. Ionizing Ionic Compound Activators/Cocatalysts

Embodiments of the present techniques may include a catalyst compositionas presented herein, that also includes an optional ionizing ioniccompound as an activator and/or cocatalyst in addition to othercomponents. Examples of such ionizing ionic compounds are disclosed inU.S. Pat. Nos. 5,576,259 and 5,807,938 which are herein incorporated byreference in their entirety herein.

An ionizing ionic compound is an ionic compound which can function toenhance activity of the catalyst composition. While not intending to bebound by theory, it is believed that the ionizing ionic compound may becapable of reacting with the metallocene compound and converting themetallocene into a cationic metallocene compound. Again, while notintending to be bound by theory, it is believed that the ionizing ioniccompound can function as an ionizing compound by completely or partiallyextracting an anionic ligand, such as one of the non-η⁵-alkadienylligands, X³ or X⁴, from the metallocene. However, the ionizing ioniccompound is an activator regardless of whether it is ionizes themetallocene, abstracts an X³ or X⁴ ligand in a fashion as to form an ionpair, weakens the metal-(X³) or metal-(X⁴) bond in the metallocene,simply coordinates to an X³ or X⁴ ligand, or any other mechanisms bywhich activation can occur. Further, it is not necessary that theionizing ionic compound activate the metallocene only. The activationfunction of the ionizing ionic compound may be evident in the enhancedactivity of catalyst composition as a whole, as compared to a catalystcomposition containing catalyst composition that does not include anyionizing ionic compound.

Examples of ionizing ionic compounds may include, for example, suchcompounds as: tri(n-butyl)ammonium tetrakis(p-tolyl)borate,tri(n-butyl)ammonium tetrakis(m-tolyl)borate, tri(n-butyl)ammoniumtetrakis(2,4-dimethylphenyl)borate, tri(n-butyl)ammoniumtetrakis(3,5-dimethylphenyl)borate, tri(n-butyl)ammoniumtetrakis[3,5-bis(trifluoromethyl)phenyl]borate, tri(n-butyl)ammoniumtetrakis(pentafluorophenyl)borate, N,N-dimethylaniliniumtetrakis(p-tolyl)borate, N,N-dimethylanilinium tetrakis(m-tolyl)borate,N,N-dimethylanilinium tetrakis(2,4-dimethylphenyl)borate,N,N-dimethylanilinium tetrakis(3,5-dimethylphenyl)borate,N,N-dimethylanilinium tetrakis[3,5-bis(trifluoromethyl)phenyl]borate,N,N-dimethylanilinium tetrakis(pentafluorophenyl)borate,triphenylcarbenium tetrakis(p-tolyl)borate, triphenylcarbeniumtetrakis(m-tolyl)borate, triphenylcarbeniumtetrakis(2,4-dimethylphenyl)borate, triphenylcarbeniumtetrakis(3,5-dimethylphenyl)borate, triphenylcarbeniumtetrakis[3,5-bis(trifluoromethyl)phenyl]borate, triphenylcarbeniumtetrakis(pentafluorophenyl)borate, tropylium tetrakis(p-tolyl)borate,tropylium tetrakis(m-tolyl)borate, tropyliumtetrakis(2,4-dimethylphenyl)borate, tropyliumtetrakis(3,5-dimethylphenyl)borate, tropyliumtetrakis[3,5-bis(trifluoromethyl)phenyl]borate, tropyliumtetrakis(pentafluorophenyl)borate, lithiumtetrakis(pentafluorophenyl)borate, lithium tetrakis(phenyl)borate,lithium tetrakis(p-tolyl)borate, lithium tetrakis(m-tolyl)borate,lithium tetrakis(2,4-dimethylphenyl)borate, lithiumtetrakis(3,5-dimethylphenyl)borate, lithium tetrafluoroborate, sodiumtetrakis(pentafluoro-phenyl)borate, sodium tetrakis(phenyl)borate,sodium tetrakis(p-tolyl)borate, sodium tetrakis(m-tolyl)borate, sodiumtetrakis(2,4-dimethylphenyl)borate, sodiumtetrakis(3,5-dimethylphenyl)borate, sodium tetrafluoroborate, potassiumtetrakis-(pentafluorophenyl)borate, potassium tetrakis(phenyl)borate,potassium tetrakis(p-tolyl)borate, potassium tetrakis(m-tolyl)borate,potassium tetrakis(2,4-dimethyl-phenyl)borate, potassiumtetrakis(3,5-dimethylphenyl)borate, potassium tetrafluoro-borate,triphenylcarbenium tetrakis(p-tolyl)aluminate, triphenylcarbeniumtetrakis(m-tolyl)aluminate, triphenylcarbeniumtetrakis(2,4-dimethylphenyl)aluminate, triphenyl-carbeniumtetrakis(3,5-dimethylphenyl)aluminate, triphenylcarbeniumtetrakis-(pentafluorophenyl)aluminate, tropyliumtetrakis(p-tolyl)aluminate, tropylium tetrakis(m-tolyl)aluminate,tropylium tetrakis(2,4-dimethylphenyl)aluminate, tropyliumtetrakis(3,5-dimethylphenyl)aluminate, tropyliumtetrakis(pentafluorophenyl)aluminate, lithiumtetrakis(pentafluorophenyl)aluminate, lithium tetrakis(phenyl)aluminate,lithium tetrakis(p-tolyl)aluminate, lithium tetrakis(m-tolyl)aluminate,lithium tetrakis(2,4-dimethylphenyl)aluminate, lithiumtetrakis(3,5-dimethylphenyl)aluminate, lithium tetrafluoroaluminate,sodium tetrakis(pentafluorophenyl)aluminate, sodiumtetrakis(phenyl)aluminate, sodium tetrakis(p-tolyl)aluminate, sodiumtetrakis(m-tolyl)aluminate, sodiumtetrakis(2,4-dimethylphenyl)aluminate, sodiumtetrakis(3,5-dimethylphenyl)aluminate, sodium tetrafluoroaluminate,potassium tetrakis(pentafluorophenyl)aluminate, potassiumtetrakis(phenyl)aluminate, potassium tetrakis(p-tolyl)aluminate,potassium tetrakis(m-tolyl)aluminate, potassiumtetrakis(2,4-dimethylphenyl)aluminate, potassiumtetrakis(3,5-dimethylphenyl)aluminate, potassium tetrafluoroaluminate,triphenylcarbenium tris(2,2′,2″-nonafluorobiphenyl)fluoroaluminate,silver tetrakis(1,1,1,3,3,3-hexafluoro-isopropanolato)aluminate, orsilver tetrakis(perfluoro-t-butoxy)aluminate, or any combinationthereof.

D. Non-Limiting Examples of the Catalyst Composition

Exemplary catalyst compositions of the present techniques may includethe compositions described below. In embodiments, for example, thecatalyst composition may include, or the catalyst composition mayinclude the contact product of, an ansa-metallocene, an organoaluminumcompound, and an activator-support. The ansa-metallocene may includecompounds having the general formula:

In this formula, M¹ may be zirconium or hafnium and X′ and X″ may beindependently F, Cl, Br, or I. E may be C or Si and R¹ and R² may beindependently an alkyl group or an aryl group, either of which having upto 10 carbon atoms, or hydrogen. R^(3A) and R^(3B) may be independentlya hydrocarbyl group or a trihydrocarbylsilyl group, any of which havingup to 20 carbon atoms, or hydrogen. The subscript ‘n’ may be an integerfrom 0 to 10, inclusive. R^(4A) and R^(4B) may be independently ahydrocarbyl group having up to 12 carbon atoms, or hydrogen. Theorganoaluminum compound may be, for example, trimethylaluminum,triethylaluminum, tripropylaluminum, tributylaluminum,triisobutylaluminum, trihexylaluminum, triisohexylaluminum,trioctylaluminum, diethylaluminum ethoxide, diisobutylaluminum hydride,diethylaluminum chloride, or any combination thereof. In thisembodiment, the activator-support may be a solid oxide treated with anelectron-withdrawing anion, wherein the solid oxide may be, for example,silica, alumina, silica-alumina, aluminophosphate, aluminum phosphate,zinc aluminate, heteropolytungstates, titania, zirconia, magnesia,boria, zinc oxide, mixed oxides thereof, or any combination thereof. Theelectron-withdrawing anion may be, for example, fluoride, chloride,bromide, iodide, phosphate, triflate, bisulfate, sulfate, fluoroborate,fluorosulfate, trifluoroacetate, phosphate, fluorophosphate,fluorozirconate, fluorosilicate, fluorotitanate, permanganate,substituted or unsubstituted alkanesulfonate, substituted orunsubstituted arenesulfonate, substituted or unsubstituted alkylsulfate,or any combination thereof.

Alternatively, in the embodiments described above, the ansa-metallocenemay be compounds having the general formula:

In this formula, M¹ may be zirconium or hafnium and X′ and X″ may beindependently F, Cl, Br, or I. E may be C or Si and R¹ and R² may beindependently an alkyl group or an aryl group, either of which having upto 10 carbon atoms, or hydrogen. R^(3A) and R^(3B) may be independentlyH, methyl, ethyl, allyl, benzyl, butyl, pentyl, hexyl, ortrimethylsilyl. The subscript ‘n’ may be an integer from 1 to 6,inclusive. R^(4A) and R^(4B) may be independently a hydrocarbyl grouphaving up to 6 carbon atoms, or hydrogen.

Further, in the embodiments described above, the ansa-metallocene may becompounds having the general formula:

In this formula, M¹ may be zirconium or hafnium and X′ and X″ may beindependently F, Cl, Br, or I. E may be C or Si and R¹ and R² may beindependently methyl or phenyl. R^(3A) and R^(3B) may be independently Hor methyl, and the subscript ‘n’ may be 1 or 2. R^(4A) and R^(4B) may beindependently H or t-butyl. For example, in the catalyst compositiondescribed above, the ansa-metallocene may be any of (I-1) through (I-4),as shown in FIG. 1, or any combination thereof.

In exemplary embodiments, the catalyst composition may include, or thecatalyst composition may include the contact product of, anansa-metallocene, an organoaluminum compound, and an activator-support.The ansa-metallocene may be any of (I-1) through (I-4), as shown in FIG.1, or any combination thereof. The organoaluminum compound may includetriethylaluminum, tri-n-butylaluminum, triisobutylaluminum, or anycombination thereof. The activator-support may include a sulfated solidoxide.

In other embodiments, the catalyst composition may include, or thecatalyst composition may include the contact product of, anansa-metallocene, an organoaluminum compound, and an activator-support.In these embodiments the ansa-metallocene may be any of (I-1) through(I-4), as shown in FIG. 1, or any combination thereof. Theorganoaluminum compound may include triethylaluminum,tri-n-butylaluminum, triisobutylaluminum, or any combination thereof.The activator-support may include sulfated alumina.

In yet other embodiments, the catalyst composition may include, or thecatalyst composition may include the contact product of a precontactedansa-metallocene, a precontacted organoaluminum compound, a precontactedolefin, and a postcontacted activator-support, wherein each of theansa-metallocene, the organoaluminum compound, the olefin, and theactivator-support may be as presented herein.

Further embodiments of the present techniques provide a catalystcomposition that includes the contact product of a tightly-bridgedansa-metallocene compound containing an alkyl group attached to theη⁵-cyclopentadienyl-type ligand and a reagent that can function toconvert the metallocene into an active catalyst that is different fromthe combination of the solid oxide activator-support and organoaluminumcompound presented herein. Thus, in one embodiment, the active catalystcomposition may be formed by activating the metallocene, which mayinclude converting the metallocene compound to its cationic form, and byproviding it with a hydrocarbyl ligand (e.g., alkylation) before, after,or during its conversion to a cation that can initiate olefinpolymerization. The reagent that can convert the metallocene into anactive catalyst may include a component that provides an activatableligand such as an alkyl to the metallocene and an activator component,as provided herein. In some instances, both functions may be achievedwith one component, for example, an organoaluminoxane. In otherinstances, these two functions may be provided by two separatecomponents, such as an organoaluminum compound that can provide anactivatable alkyl ligand to the metallocene, and another component thatcan provide the activator function.

The activator and/or alkylation agent for the ansa-metallocene compoundmay be an organoaluminoxane, such as, for example, methylaluminoxane orisobutylaluminoxane. Alternatively, the activator may be a Lewis acidicorganoboron compound capable of abstracting an anionic ligand from themetallocene, such as, for example, tris(pentafluorophenyl)boron ortriphenylcarbenium tetrakis(pentafluorophenyl)borate, that may be usedin combination with an alkylating agent such as an organoaluminumcompound.

Further, a dialkylated tightly-bridged ansa-metallocene compound aspresented herein may be reacted with a Brønsted acidic borate activatorsuch as tri(n-butyl)ammonium tetrakis(p-tolyl)borate orN,N-dimethylanilinium tetrakis-(pentafluorophenyl)borate to remove onealkyl ligand to form an alkylated metallocene cation. Alternatively, thedialkylated tightly-bridged ansa-metallocene compound may be reactedwith a Lewis acid borate activator such as triphenylcarbeniumtetrakis(pentafluorophenyl)borate to remove one alkyl ligand to form analkylated metallocene cation. Thus, while not intending to be bound bytheory, it is believed that the active catalyst may include an alkylatedmetallocene cation, and any number of alternate reactions may be used togenerate such a catalyst.

The present techniques may include a catalyst composition that containsa contact product of a tightly-bridged ansa-metallocene which includes ahydrocarbyl ligand that can initiate olefin polymerization and a solidoxide activator-support, without the need for the addition of anorganoaluminum compound. The ansa-metallocene compound may include apendant alkyl group attached to one of the η⁵-cyclopentadienyl-typeligand, and a hydrocarbyl ligand that can initiate olefinpolymerization. An organoaluminum compound may not be required toalkylate this type of “pre-alkylated” ansa-metallocene because italready includes a hydrocarbyl ligand that can initiate olefinpolymerization.

E. The Olefin Monomer

In the present techniques, various unsaturated reactants may be usefulin the polymerization processes with catalyst compositions andprocesses. Such reactants include olefin compounds having from about 2to about 30 carbon atoms per molecule and having an olefinic doublebond. The present techniques encompass homopolymerization processesusing a single olefin such as ethylene or propylene, as well ascopolymerization reactions with two or more different olefiniccompounds. For example, in a copolymerization reaction with ethylene,copolymers may include a major amount of ethylene (>50 mole percent) anda minor amount of comonomer <50 mole percent. The comonomers that may becopolymerized with ethylene may have from three to about 20 carbon atomsin their molecular chain.

Olefins that may be used as monomer or comonomer include acyclic,cyclic, polycyclic, terminal (α), internal, linear, branched,substituted, unsubstituted, functionalized, and non-functionalizedolefins. For example, compounds that may be polymerized with thecatalysts of the present techniques include propylene, 1-butene,2-butene, 3-methyl-1-butene, isobutylene, 1-pentene, 2-pentene,3-methyl-1-pentene, 4-methyl-1-pentene, 1-hexene, 2-hexene, 3-hexene,3-ethyl-1-hexene, 1-heptene, 2-heptene, 3-heptene, the four normaloctenes, the four normal nonenes, the five normal decenes, or anycombination thereof. Further, cyclic and bicyclic olefins, including,for example, cyclopentene, cyclohexene, norbornylene, norbornadiene, andthe like, may also be polymerized as described above.

The amount of comonomer introduced into a reactor zone to produce acopolymer may be from about 0.001 to about 99 weight percent comonomerbased on the total weight of the monomer and comonomer, generally fromabout 0.01 to about 50 weight percent. In other embodiments, the amountof comonomer introduced into a reactor zone may be from about 0.01 toabout 10 weight percent comonomer or from about 0.1 to about 5 weightpercent comonomer. Alternatively, an amount sufficient to give the abovedescribed concentrations, by weight, of the copolymer produced, may beused.

While not intending to be bound by theory, it is believed that sterichindrance can impede or slow the polymerization process if branched,substituted, or functionalized olefins are used as reactants. However,if the branched and/or cyclic portion(s) of the olefin are somewhatremoved from the carbon-carbon double bond they would not be expected tohinder the reaction as much as more proximate substituents.

In exemplary embodiments, a reactant for the catalyst compositions ofthe present techniques is ethylene, so the polymerizations may be eitherhomopolymerizations or copolymerizations with a different acyclic,cyclic, terminal, internal, linear, branched, substituted, orunsubstituted olefin. In addition, the catalyst compositions of thepresent techniques may be used in polymerization of diolefin compounds,including for example, such compounds as 1,3-butadiene, isoprene,1,4-pentadiene, and 1,5-hexadiene.

II. Preparation of the Catalyst Composition

The present techniques encompass a catalyst composition and a methodthat includes contacting a tightly-bridged ansa-metallocene compound, anactivator, and optionally an organoaluminum compound, as presentedherein. The method presented herein encompasses any series of contactingsteps that allows contacting each of the components including any orderof contacting components or mixtures of components. While not intendingto be limiting, examples of contacting steps may be exemplified using atreated solid oxide activator-support and an organoaluminum cocatalyst.These steps may encompass any number of precontacting and postcontactingsteps, and may further encompass using an olefin monomer as a contactcomponent in any of these steps. Examples of methods to prepare thecatalyst composition of the present techniques are discussed below.

A. Precontacting the Catalyst Composition with an Olefin

Precontacting a catalyst composition, or a component of a catalystcomposition, with an olefinic monomer prior to adding the catalystcomposition to a reactor may increase the productivity of the polymer ascompared to the same catalyst composition that is prepared without aprecontacting step. The enhanced activity catalyst composition of thepresent techniques may be used for homopolymerization of an α-olefinmonomer such as ethylene or copolymerization of an α-olefin and acomonomer. However, a precontacting step is not required for thecatalyst compositions of the present techniques.

In some embodiments of the present techniques, the ansa-metallocene maybe precontacted with an olefinic monomer, although not necessarily theolefin monomer to be polymerized, and an organoaluminum cocatalyst for afirst period of time. This precontacted mixture may then be contactedwith the solid oxide activator-support. For example, the first period oftime for contact, the precontact time, between the ansa-metallocene, theolefinic monomer, and the organoaluminum cocatalyst may range in timefrom about 1 minute to about 24 hours, from about 0.1 to about 1 hour,or from about 10 minutes to about 30 minutes.

Once the precontacted mixture of ansa-metallocene, olefin monomer, andorganoaluminum cocatalyst is contacted with the solid oxide activator,this composition (further including the solid oxide activator) may betermed the postcontacted mixture. The postcontacted mixture may beallowed to remain in contact for a second period of time, thepostcontact time, prior to being used in the polymerization process.This may provide increases in activity in a similar fashion toprecontacting the catalyst composition. Postcontact times between thesolid oxide activator-support and the precontacted mixture may range intime from about 1 minute to about 24 hours, from 0.1 hours to about 1hour, or from about 10 minutes to about 30 minutes.

The various catalyst components (for example, ansa-metallocene,activator-support, organoaluminum cocatalyst, and optionally anunsaturated hydrocarbon) may be contacted in the polymerization reactorsimultaneously while the polymerization reaction is proceeding.Alternatively, any two or more of these catalyst components may beprecontacted in a vessel or tube prior to their entering the reactionzone. This precontacting step may be a continuous process, in which theprecontacted product may be fed continuously to the reactor, or it maybe a stepwise or batchwise process in which a batch of precontactedproduct may be added to make a catalyst composition. This precontactingstep may be carried out over a time period that may range from a fewseconds to as much as several days, or longer. For example, thecontinuous precontacting step may last from about 1 second to about 1hour, from about 10 seconds to about 45 minutes, or from about 1 minuteto about 30 minutes.

B. Multiple Precontacting Steps

Alternatively the precontacting process may be carried out in multiplesteps, rather than a single step, in which multiple mixtures areprepared, each including a different set of catalyst components. Forexample, at least two catalyst components may be contacted forming afirst mixture, followed by contacting the first mixture with anothercatalyst component forming a second mixture, and so forth.

Multiple precontacting steps may be carried out in a single vessel or inmultiple vessels. Further, multiple precontacting steps may be carriedout in series (sequentially), in parallel, or a combination thereof. Forexample, a first mixture of two catalyst components may be formed in afirst vessel, a second mixture including the first mixture plus oneadditional catalyst component may be formed in the first vessel or in asecond vessel, which may be placed downstream of the first vessel.

One or more of the catalyst components may be split and used indifferent precontacting treatments. For example, part of a catalystcomponent may be fed into a first precontacting vessel for precontactingwith another catalyst component, while the remainder of that samecatalyst component may be fed into a second precontacting vessel forprecontacting with another catalyst component, or may be fed directlyinto the reactor, or a combination thereof. The precontacting may becarried out in any suitable equipment, such as tanks, stirred mix tanks,various static mixing devices, a tube, a flask, a vessel of any type, orany combination thereof. For example, a catalyst composition of thepresent techniques may be prepared by contacting 1-hexene,triisobutylaluminum or tri-n-butylaluminum, and an ansa-metallocene forat least about 30 minutes, followed by contacting the precontactedmixture with a sulfated alumina activator-support for at least about 10minutes up to one hour to form the active catalyst.

The postcontacted mixture may be heated at a temperature and for a timesufficient to allow adsorption, impregnation, or interaction ofprecontacted mixture and the solid oxide activator-support, such that aportion of the components of the precontacted mixture may beimmobilized, adsorbed, or deposited thereon. For example, thepostcontacted mixture may be heated from between about 0° F. to about150° F., or from between about 40° F. to about 95° F. Neither aprecontacting step nor a postcontacting step may be required for thepresent techniques.

C. Composition Ratios for Catalyst Compositions

In embodiments of the present techniques, the molar ratio of theansa-metallocene compound to the organoaluminum compound may be fromabout 1:1 to about 1:10,000 (e.g., about 1:2, 1:5, 1:20, 1:50, 1:200,1:500, 1:2000, 1:5000, 1:8000, etc.), from about 1:1 to about 1:1,000,or from about 1:1 to about 1:100. These molar ratios reflect the ratioof ansa-metallocene compound to the total amount of organoaluminumcompound in both the precontacted mixture and the postcontacted mixture,combined.

When a precontacting step is used, the molar ratio of olefin monomer toansa-metallocene compound in the precontacted mixture may be from about1:10 to about 100,000:1 (e.g., 1:10, 1:5, 1:1, 5:1, 5000:1, 10,000:1,50,000:1, etc.), or from about 10:1 to about 1,000:1. The weight ratioof the solid oxide activator to the organoaluminum compound may rangefrom about 1:5 to about 1,000:1, from about 1:3 to about 100:1, or fromabout 1:1 to about 50:1. The weight ratio of the ansa-metallocene tosolid oxide activator-support may be from about 1:1 to about 1:1,000,000(e.g., 1:2, 1:10, 1:5,000, 1:100,000, etc.), from about 1:10 to about1:100,000, or from about 1:20 to about 1:1000.

D. Examples of a Process to Prepare a Catalyst Composition

Embodiments of the present techniques include processes to produce acatalyst composition. For example, one such process may includecontacting an ansa-metallocene, an olefin, and an organoaluminumcompound for a first period of time to form a precontacted mixtureincluding a precontacted ansa-metallocene, a precontacted organoaluminumcompound, and a precontacted olefin. The precontacted mixture may thenbe contacted with an activator-support and optionally additionalorganoaluminum compound for a second period of time to form apostcontacted mixture including a postcontacted ansa-metallocene, apostcontacted organoaluminum compound, a postcontacted olefin, and apostcontacted activator-support. In embodiments, the ansa-metallocenemay include a compound having the formula:(X¹)(X²)(X³)(X⁴)M¹,in which M¹ may be titanium, zirconium, or hafnium. X¹ may be asubstituted cyclopentadienyl, a substituted indenyl, or a substitutedfluorenyl. X² may be a substituted cyclopentadienyl or a substitutedfluorenyl.

One substituent on X¹ and X² is a bridging group having the formulaER¹R², in which E may be a carbon atom, a silicon atom, a germaniumatom, or a tin atom. E is bonded to both X¹ and X². R¹ and R² may beindependently an alkyl group or an aryl group, either of which having upto 12 carbon atoms, or hydrogen. One substituent on X² is a substitutedor an unsubstituted alkyl group having up to 12 carbon atoms.

X³ and X⁴ may be independently: 1) F, Cl, Br, or I; 2) a hydrocarbylgroup having up to 20 carbon atoms, H, or BH₄; 3) a hydrocarbyloxidegroup, a hydrocarbylamino group, or a trihydrocarbylsilyl group, any ofwhich having up to 20 carbon atoms; 4) OBR^(A) ₂ or SO₃R^(A), whereinR^(A) may be an alkyl group or an aryl group, any of which having up to12 carbon atoms.

Any additional substituent on the substituted cyclopentadienyl,substituted indenyl, substituted fluorenyl, or substituted alkyl groupmay be independently an aliphatic group, an aromatic group, a cyclicgroup, a combination of aliphatic and cyclic groups, an oxygen group, asulfur group, a nitrogen group, a phosphorus group, an arsenic group, acarbon group, a silicon group, or a boron group, any of which havingfrom 1 to 20 carbon atoms; a halide; or hydrogen.

E. Activity of the Catalyst Composition

The catalytic activity of the catalyst of the present techniques may begreater than or equal to about 1000 grams polyethylene per gram ofchemically treated solid oxide per hour (abbreviated gP/(g CTSO·hr)),greater than or equal to about 3000 gP/(g CTSO·hr), greater than orequal to about 6000 gP/(g CTSO·hr), or greater than or equal to about9000 gP/(g CTSO·hr). Activity may be measured under slurrypolymerization conditions using isobutane as the diluent, with apolymerization temperature from about 80° C. to about 100° C., and anethylene pressure of about 340 psig to about 450 psig. The reactorshould have substantially no indication of any wall scale, coating orother forms of fouling when making these measurements.

III. Use of the Catalyst Composition in Polymerization Processes

The catalysts of the present techniques are intended for any olefinpolymerization method, using various types of polymerization reactors.As used herein, “polymerization reactor” includes any polymerizationreactor capable of polymerizing olefin monomers to produce homopolymersor copolymers. Such homopolymers and copolymers may be referred to asresins or polymers. The various types of reactors include those that maybe referred to as batch, slurry, gas-phase, solution, high pressure,tubular or autoclave reactors. Gas phase reactors may include fluidizedbed reactors or staged horizontal reactors. Slurry reactors may includevertical or horizontal loops. High pressure reactors may includeautoclave or tubular reactors. Reactor types may include batch orcontinuous processes. Continuous processes could use intermittent orcontinuous product discharge. Processes may also include partial or fulldirect recycle of un-reacted monomer, un-reacted comonomer, and/ordiluent.

Polymerization reactor systems of the present techniques may include onetype of reactor in a system or multiple reactors of the same ordifferent type. Production of polymers in multiple reactors may includeseveral stages in at least two separate polymerization reactorsinterconnected by a transfer device making it possible to transfer thepolymers resulting from the first polymerization reactor into the secondreactor. The desired polymerization conditions in one of the reactorsmay be different from the operating conditions of the other reactors.Alternatively, polymerization in multiple reactors may include themanual transfer of polymer from one reactor to subsequent reactors forcontinued polymerization. Multiple reactor systems may include anycombination including, but not limited to, multiple loop reactors,multiple gas reactors, a combination of loop and gas reactors, multiplehigh pressure reactors or a combination of high pressure with loopand/or gas reactors. The multiple reactors may be operated in series orin parallel.

A. Loop Slurry Polymerization Processes

In embodiments of the present techniques, the polymerization reactorsystem may include a loop slurry reactor. Such reactors may includevertical or horizontal loops. Monomer, diluent, catalyst and optionallyany comonomer may be continuously fed to the loop reactor wherepolymerization occurs. Generally, continuous processes may include thecontinuous introduction of a monomer, a catalyst, and a diluent into apolymerization reactor and the continuous removal from this reactor of asuspension including polymer particles and the diluent. Reactor effluentmay be flashed to remove the solid polymer from the liquids that includethe diluent, monomer and/or comonomer. Various technologies may beemployed for this separation step including but not limited to, flashingthat may include any combination of heat addition and pressurereduction; separation by cyclonic action in either a cyclone orhydrocyclone; or separation by centrifugation.

Loop slurry polymerization processes (also known as the particle formprocess) are disclosed, for example, in U.S. Pat. Nos. 3,248,179,4,501,885, 5,565,175, 5,575,979, 6,239,235, 6,262,191 and 6,833,415,each of which is incorporated by reference in its entirety herein.

Diluents that may be used in slurry polymerization include, for example,the monomer being polymerized and hydrocarbons that are liquids underreaction conditions. Examples of such diluents may include, for example,hydrocarbons such as propane, cyclohexane, isobutane, n-butane,n-pentane, isopentane, neopentane, and n-hexane. Some looppolymerization reactions can occur under bulk conditions where nodiluent may be used or where the monomer (e.g., propylene) acts as thediluent. An example is polymerization of propylene monomer as disclosedin U.S. Pat. No. 5,455,314, which is incorporated by reference in itsentirety herein.

B. Gas Phase Polymerization Processes

Further, the polymerization reactor may include a gas phase reactor.Such systems may employ a continuous recycle stream containing one ormore monomers continuously cycled through a fluidized bed in thepresence of the catalyst under polymerization conditions. A recyclestream may be withdrawn from the fluidized bed and recycled back intothe reactor. Simultaneously, polymer product may be withdrawn from thereactor and new or fresh monomer may be added to replace the polymerizedmonomer. Such gas phase reactors may include a process for multi-stepgas-phase polymerization of olefins, in which olefins are polymerized inthe gaseous phase in at least two independent gas-phase polymerizationzones while feeding a catalyst-containing polymer formed in a firstpolymerization zone to a second polymerization zone. One type of gasphase reactor is disclosed in U.S. Pat. Nos. 5,352,749, 4,588,790 and5,436,304, each of which is incorporated by reference in its entiretyherein.

According to still another aspect of the techniques, a high pressurepolymerization reactor may include a tubular reactor or an autoclavereactor. Tubular reactors may have several zones where fresh monomer,initiators, or catalysts are added. Monomer may be entrained in an inertgaseous stream and introduced at one zone of the reactor. Initiators,catalysts, and/or catalyst components may be entrained in a gaseousstream and introduced at another zone of the reactor. The gas streamsmay be intermixed for polymerization. Heat and pressure may be employedappropriately to obtain optimal polymerization reaction conditions.

C. Solution Polymerization Processes

According to yet another aspect of the techniques, the polymerizationreactor may include a solution polymerization reactor wherein themonomer is contacted with the catalyst composition by suitable stirringor other means. A carrier including an inert organic diluent or excessmonomer may be employed. If desired, the monomer may be brought in thevapor phase into contact with the catalytic reaction product, in thepresence or absence of liquid material. The polymerization zone may bemaintained at temperatures and pressures that will result in theformation of a solution of the polymer in a reaction medium. Agitationmay be employed to obtain better temperature control and to maintainuniform polymerization mixtures throughout the polymerization zone.Adequate means may be utilized for dissipating the exothermic heat ofpolymerization.

D. Reactor Support Systems

Polymerization reactors suitable for the present techniques may furtherinclude any combination of a raw material feed system, a feed system forcatalyst or catalyst components, and/or a polymer recovery system. Suchsystems may include systems for feedstock purification, catalyst storageand preparation, extrusion, reactor cooling, polymer recovery,fractionation, recycle, storage, loadout, laboratory analysis, andprocess control, among others.

E. Polymerization Conditions

Conditions that may be controlled for polymerization efficiency and toprovide resin properties include temperature, pressure and theconcentrations of various reactants. Polymerization temperature canaffect catalyst productivity, polymer molecular weight and molecularweight distribution. Suitable polymerization temperature may be anytemperature below the de-polymerization temperature according to theGibbs Free energy equation. Typically this includes from about 60° C. toabout 280° C., for example, and from about 70° C. to about 110° C.,depending upon the type of polymerization reactor.

Suitable pressures will also vary according to the reactor andpolymerization type. The pressure for liquid phase polymerizations in aloop reactor is typically less than 1000 psig. Pressure for gas phasepolymerization is usually at about 200-500 psig. High pressurepolymerization in tubular or autoclave reactors is generally run atabout 20,000 to 75,000 psig. Polymerization reactors may also beoperated in a supercritical region occurring at generally highertemperatures and pressures. Operation above the critical point of apressure/temperature diagram (supercritical phase) may offer advantages.

The concentration of various reactants may be controlled to produceresins with certain physical and mechanical properties. The proposedend-use product that will be formed by the resin and the method offorming that product determines the desired resin properties. Mechanicalproperties include tensile, flexural, impact, creep, stress relaxationand hardness tests. Physical properties include density, molecularweight, molecular weight distribution, melting temperature, glasstransition temperature, temperature melt of crystallization, density,stereoregularity, crack growth, long chain branching and rheologicalmeasurements.

The concentrations of monomer, co-monomer, hydrogen, co-catalyst,modifiers, and electron donors may be important in producing these resinproperties. Comonomer may be used to control product density. Hydrogenmay be used to control product molecular weight. Co-catalysts may beused to alkylate, scavenge poisons and control molecular weight.Modifiers may be used to control product properties and electron donorsaffect stereoregularity. In addition, the concentration of poisons mustbe minimized since they impact the reactions and product properties.

F. Final Products Made from Polymers

The polymer or resin fluff from the reactor system may have additivesand modifiers added to provide better processing during manufacturingand for desired properties in the end product. Additives include surfacemodifiers such as slip agents, antiblocks, tackifiers; antioxidants suchas primary and secondary antioxidants; pigments; processing aids such aswaxes/oils and fluoroelastomers; and special additives such as fireretardants, antistats, scavengers, absorbers, odor enhancers, anddegradation agents. After the addition of the additives, the polymer orresin fluff may be extruded and formed into pellets for distribution tocustomers and formation into final end-products.

To form end-products or components from the pellets, the pellets aregenerally subjected to further processing, such as blow molding,injection molding, rotational molding, blown film, cast film, extrusion(e.g., sheet extrusion, pipe and corrugated extrusion,coating/lamination extrusion, etc.), and so on. Blow molding is aprocess used for producing hollow plastic parts. The process typicallyemploys blow molding equipment, such as reciprocating screw machines,accumulator head machines, and so on. The blow molding process may betailored to meet the customer's needs, and to manufacture productsranging from the plastic milk bottles to the automotive fuel tanksmentioned above. Similarly, in injection molding, products andcomponents may be molded for a wide range of applications, includingcontainers, food and chemical packaging, toys, automotive, crates, capsand closures, to name a few.

Profile extrusion processes may also be used. Polyethylene pipe, forexample, may be extruded from polyethylene pellet resins and used in anassortment of applications due to its chemical resistance, relative easeof installation, durability and cost advantages, and the like. Indeed,plastic polyethylene piping has achieved significant use for watermains, gas distribution, storm and sanitary sewers, interior plumbing,electrical conduits, power and communications ducts, chilled waterpiping, and well casings, among others. In particular, high-densitypolyethylene (HDPE), which generally constitutes the largest volume ofthe polyolefin group of plastics used for pipe, is tough,abrasion-resistant and flexible (even at subfreezing temperatures).Furthermore, HDPE pipe may be used in small diameter tubing and in pipeup to more than 8 feet in diameter. In general, polyethylene pellets(resins) may be supplied for the pressure piping markets, such as innatural gas distribution, and for the non-pressure piping markets, suchas for conduit and corrugated piping.

Rotational molding is a high-temperature, low-pressure process used toform hollow parts through the application of heat to biaxially-rotatedmolds. Polyethylene pellet resins generally applicable in this processare those resins that flow together in the absence of pressure whenmelted to form a bubble-free part. Resins, such as those produced by thecatalyst compositions of the present techniques, may offer such flowcharacteristics, as well as a wide processing window. Furthermore, thesepolyethylene resins suitable for rotational molding may exhibitdesirable low-temperature impact strength, good load-bearing properties,and good ultraviolet (UV) stability. Accordingly, applications forrotationally-molded polyolefin resins include agricultural tanks,industrial chemical tanks, potable water storage tanks, industrial wastecontainers, recreational equipment, marine products, plus many more.

Sheet extrusion is a technique for making flat plastic sheets from avariety of resins. The relatively thin gauge sheets are generallythermoformed into packaging applications such as drink cups, delicontainers, produce trays, baby wipe containers and margarine tubs.Other markets for sheet extrusion of polyolefin include those thatutilize relatively thicker sheets for industrial and recreationalapplications, such as truck bed liners, pallets, automotive dunnage,playground equipment, and boats. A third use for extruded sheet, forexample, is in geomembranes, where flat-sheet polyethylene material maybe welded into large containment systems for mining applications andmunicipal waste disposal.

The blown film process is a relatively diverse conversion system usedfor polyethylene. The American Society for Testing and Materials (ASTM)defines films as less than 0.254 millimeter (10 mils) in thickness.However, the blown film process can produce materials as thick as 0.5millimeter (20 mils), and higher. Furthermore, blow molding inconjunction with monolayer and/or multilayer coextrusion technologieslays the groundwork for several applications. Advantageous properties ofthe blow molding products may include clarity, strength, tearability,optical properties, and toughness, to name a few. Applications mayinclude food and retail packaging, industrial packaging, andnon-packaging applications, such as agricultural films, hygiene film,and so forth.

The cast film process may differ from the blown film process through thefast quench and virtual unidirectional orientation capabilities. Thesecharacteristics allow a cast film line, for example, to operate athigher production rates while producing beneficial optics. Applicationsin food and retail packaging take advantage of these strengths. Finally,polyolefin pellets may also be supplied for the extrusion coating andlamination industry.

Ultimately, the products and components formed from polyolefin (e.g.,polyethylene) pellets may be further processed and assembled fordistribution and sale to the consumer. For example, a polyethylene milkbottle may be filled with milk for distribution to the consumer, or thefuel tank may be assembled into an automobile for distribution and saleto the consumer.

IV. Examples of Polymers Prepared Using the Catalysts of the PresentTechniques

Without intending to be limiting, ethylene polymers produced usingcatalyst compositions of the present techniques may be characterized bylower melt elasticity than may be observed when using tightly-bridgedansa-metallocene catalysts without an alkyl group bonded to aη⁵-cyclopentadienyl-type ligand. This may be demonstrated by thepolymerization runs shown in Tables 1 and 2. Further, as shown in Table1, the low steric hindrance from the linear alkyl substituent on theη⁵-cyclopentadienyl-type rings may increase both activity and comonomerincorporation in some circumstances.

Specifically, metallocene R-1, which has an unsubstituted alkanesubstituent on a η⁵-indenyl ring, as shown in FIG. 2, shows higheractivity, 437 g PE/mg metallocene, and higher comonomer incorporation,0.94 mol %, than a catalyst having a bulky trimethyl silyl in the sameposition on the η⁵-indenyl. This metallocene, shown as R-2 in FIG. 2,only has an activity of 171 g PE/mg metallocene, and a comonomerincorporation of 0.5 mol %. Thus, although the catalysts of the currenttechniques may be used with any of the substituents presented herein,the examples discussed below with respect to Table 2 focus on the use ofunsubstituted alkyl groups as substituents.

TABLE 1 Comparison of hexene incorporation by catalysts having bulkysubstituents vs. linear substituents. Metall- ocene Activator-Activator- TIBAL Solid Butyl Metall- Weight Time Temp. P Hexene SupportSupport (1M) PE Branch Exam. ocene (mg) (min) (C.) (psig) (g) Type (mg)(mL) (g) (mol %) 1 R-1 1 30 80 450 25.0 Fluorided 100 0.5 437 0.94Silica Alumina 2 R-2 1 30 80 450 25.0 Fluorided 100 0.5 171 0.50 SilicaAlumina

Examples 3-15 in Table 2 show results that may be obtained for polymersmade using the catalysts of the present techniques. The specificmetallocene structures used are shown in FIG. 1, corresponding to theidentification given in the column labeled “Metallocene,” in Table 2. Incomparison, Examples 16-18 in Table 2 show results that may be obtainedfor polymers made from a catalyst having no substituents on thecyclopentadienyl rings. The metallocene structure used for these runs isshown in FIG. 2 as structure “C-1.” A further comparison may be made tocommercially available polymers used in similar applications. Analysisresults for a selection of these types of polymers are shown in Table 3.

A. Melt Elasticity

Melt elasticity may be measured by any number of rheological procedures.In one technique, as discussed below, a highly reproducible measurementof melt viscosity may be obtained from dynamic rheological measurements.The data obtained from these measurements may used to calculate a valuefor Tan δ, which is the ratio of the viscous modulus, G″, divided by theelastic modulus, G′. As the melt elasticity decreases, G″ increases andG′ decreases, increasing the value of Tan δ.

Comparing the melt elasticity of different polymers may be mostmeaningful when the melt elasticity is correlated to the molecularweight. However, the unsubstituted metallocene catalyst, the structureof which is shown as C-1 in FIG. 2, generated a significant amount ofinsoluble material, preventing measurement of the molecular weights.This is indicated by the term “insolubles,” in Examples 16-18. Thus,comparisons of Tan δ vs. Molecular weight, as discussed below, wereimpossible. As shown in Table 2, polymers made using exemplary catalystsof the present techniques, shown as I-1-I-4 in FIG. 1, all have highervalues for Tan δ than the value obtained for Example 18, which was madeusing the unsubstituted. No such comparisons were available for Examples16 and 17, as the melt elasticity for these samples was too high toallow for a meaningful measurement of Tan δ.

Accordingly, to obtain meaningful control samples for comparisons of themelt elasticity, a variety of commercial resins were analyzed using therheological techniques discussed above, with the results as shown inTable 3. The results obtained were plotted against molecular weight, asshown in FIG. 3. As can be seen in this log-log plot polymers producedusing exemplary catalysts of the present techniques have higher valuesfor Tan δ at comparable molecular weights to the control samples. Thisindicates that the melt elasticity is lower for exemplary polymershaving the same molecular weight as the control polymers.

B. Results for Molecular Weight and Activity

In addition to generating polymers that may have lower melt elasticityand no insoluble components, catalysts of the present techniques mayalso have higher activities than unsubstituted metallocenes. As seen inTable 2, the activity of exemplary catalysts of the present techniquesmay range from about 1500 g P/g CTSO·hr (grams polyethylene per gramschemically treated solid oxide per hour) up to at least about 9000 g P/gCTSO·hr. By comparison, under similar conditions, the activity of anunsubstituted metallocene, shown as C-1 in FIG. 2, ranged from about 300to about 600 g P/g CTSO·hr.

TABLE 2 Polymerization examples. Metall- Tanδ Activity Temper- ReactorSupport ocene Solid (at (g P/ (g Exam- Metall- Time ature pressureSupport weight R3A1 weight PE Mn/ Mw/ Mz/ Mw/ 0.1/ CTSO · ple ocene(min) (C.) (psi) Type (mg) (mmol) (mg) (g) 1000 1000 1000 Mn sec) hr)  3I-1 60 95  450 S-SSA¹ 100   0.25 3.0 159.0 431.96 1124.28 2486.16 2.6  0.8173 1590 TNBAL  4 I-1 60 95  450 S-SSA  200   0.25 3.0 405.0 256.57 725.57 1634.92 2.83  1.3400 2025 TNBAL  5 I-2 25 90  450 S-SSA  100  0.5  1.0 295.0 230.42  547.01 1103.58 2.37  2.1430 7080 TNBAL  6 I-2 3090  450 S-SSA  100   0.5  0.5 245.0 293.73  677.17 1288.15 2.31  1.54404900 TNBAL  7 I-2 30 80  450 S-SSA  100   0.25 1.0 150.0 409.16  999.822078.94 2.44  0.8280 3000 TNBAL  8 I-2 30 90  390 S-SSA  100   0.5  0.5130.0 314.42  759.98 1526.1  2.42  1.5320 2600 TNBAL  9 I-2 30 95  420S-SSA  100   0.5  0.5 161.0 270.4  635.42 1226.16 2.35  1.9470 3220TNBAL 10 I-2 30 100 450 S-SSA  100   0.5  1.0 454.0 182.47  417.94 792.18 2.29  3.5290 9080 TNBAL 11 I-2 30 90  420 S-SSA  100   0.5  0.5176.0 292.79  635.38 1128.92 2.17  1.6670 3520 TNBAL 12 I-3 30 90  450S-SSA  100   0.5  0.5 335.0  76.08 179.1  357.66 2.35 11.8800 6700 TNBAL13 I-3 30 90  390 S-SSA  100   0.5  0.5 224.0  85.56  188.11  352.042.2  10.0400 4480 TNBAL 14 I-3 60 80  340 S-SSA  100   0.5  0.5 225.0 94.38  291.56  603.02 3.09  4.9050 2250 TNBAL 15 I-4 30 90  450 S-SSA 100   0.5  1.0 228   306.72 732.5 1320.63 2.39  1.3710 4560 TNBAL 16 C-160 90  450 S-SSA  100   0.25 2.0 42  insol- insol- insol- insol- —  420TNBAL ubles ubles ubles ubles 17 C-1 60 105 450 S-SSA  100   0.25 2.063  insol- insol- insol- insol- —  630 TNBAL ubles ubles ubles ubles 18C-1 60 90  450 S-SSA  200.0 0.5  2.0 57  insol- insol- insol- insol- 0.3982  285 TNBAL ubles ubles ubles ubles

The activity of the catalysts may also be affected by the type ofsubstituents on the bridging substituent between the twocyclopentadienyl rings. As shown by the comparison of the activitiesseen for Examples 5-11, made using catalyst I-2, with Examples 12-14using catalyst I-3, phenyl rings on the bridging substituent maydecrease the activity.

TABLE 3 Analysis Results for Commercial PE resins made from Crcatalysts. Tanδ Example Mn/1000 Mw/1000 Mz/1000 Mw/Mn (at 0.1/sec) 1919.18 134.92 775.76 7.03 1.6130 20 18.17 140.57 927.05 7.74 1.5840 2121.65 133.61 751.41 6.17 1.4890 22 21.2 216.41 2086.1 10.21 1.1980 2314.62 354.38 3536.4 24.24 1.2740 24 14.03 303.53 2261.36 21.63 1.0330V. ProceduresA. Molecular Weight Determination

Molecular weight and molecular weight distributions were obtained usinga PL-GPC 220 (Polymer Labs, UK) system equipped with a differentialrefractive index detector and three 7.5 mm×300 mm 20 um Mixed A-LScolumns (Polymer Labs) running at 145° C. The flow rate of the mobilephase, 1,2,4-trichlorobenzene (TCB) containing 0.5 g/L2,6-di-t-butyl-4-methylphenol (BHT), was set at 1 mL/min and theconcentration of polymer solutions was generally kept in the range of1.0-1.5 mg/mL, depending on the molecular weights. Sample preparationwas conducted at 150° C. for 4 h with occasional and gentle agitationbefore the solutions being transferred to sample vials for injection. Inorder to minimize unbalanced solvent peak, solvent with the samecomposition as the mobile phase was used for solution preparation. Theintegral calibration method was used to deduce molecular weights andmolecular weight distributions using a Chevron Phillips ChemicalsCompany's linear polyethylene, Marlex BHB5003, as the broad standard.The integral table of the broad standard was pre-determined in aseparate experiment with SEC-MALS.

B. Absolute Molecular Weight as Determined by SEC-MALS

Absolute molecular weight data were determined using SEC-MALS, whichcombines the methods of size exclusion chromatography (SEC) withmulti-angle light scattering (MALS) detection. A DAWN EOS 18-angle lightscattering photometer (Wyatt Technology, Santa Barbara, Calif.) wasattached to a PL-210 SEC system (Polymer Labs, UK) or a Waters 150 CVPlus system (Milford, Mass.) through a hot transfer line, thermallycontrolled at the same temperature as the SEC columns and itsdifferential refractive index (DRI) detector (145° C.). At a flow ratesetting of 0.7 mL/min, the mobile phase, 1,2,4-trichlorobenzene (TCB),was eluted through three, 7.5 mm×300 mm, 20 μm Mixed A-LS columns(Polymer Labs). Polyethylene (PE) solutions with concentrations of ˜1.2mg/mL, depending on samples, were prepared at 150° C. for 4 h beforebeing transferred to the SEC injection vials sitting in a carouselheated at 145° C. For polymers of higher molecular weight, longerheating times were necessary in order to obtain true homogeneoussolutions. In addition to acquiring a concentration chromatogram,seventeen light-scattering chromatograms at different angles were alsoacquired for each injection using Wyatt's Astra® software. At eachchromatographic slice, both the absolute molecular weight (M) and rootmean square (RMS) radius, also known as radius of gyration (R_(g)) wereobtained from a Debye plot's intercept and slope, respectively. Methodsfor this process are detailed in Wyatt, P. J., Anal. Chim. Acta, 272, 1(1993), which is hereby incorporated herein by reference in itsentirety. The linear PE control employed was a linear, high-densitybroad molecular weight distribution (MWD) polyethylene sample (ChevronPhillips Chemical Co.). The weight average molecular weight (M_(w)),number average molecular weight (M_(n)), z-average molecular weight(M_(z)) and molecular weight distribution (M_(w)/M_(n)) were computedfrom these data, and were used to build an integral table as a controlfor the relative molecular weight determination discussed above.

C. Pore Size Determination

A Quantachrome Autosorb-6 Nitrogen Pore Size Distribution Instrument wasused to determine specific surface area (“surface area”) and specificpore volume (“pore volume”). This instrument was acquired from theQuantachrome Corporation, Syosset, N.Y.

D. Measurement of Tan δ by Rheology

Small-strain oscillatory shear measurements were performed on an ARESoscillatory rheometer using parallel-plate geometry (TA Instruments,formerly Rheometrics Inc.). Data were typically obtained over an angularfrequency range of 0.03 to 100 rad/s at a temperature of 190° C.

Fluff samples were stabilized with 0.1 wt % BHT dispersed in acetone andthen vacuum dried before molding. Samples were compression molded at184° C. for a total of three minutes. The samples were allowed to meltat a relatively low pressure for one minute and then subjected to a highmolding pressure for an additional two minutes. The molded samples werethen quenched in a cold (room temperature) press. Disks having the size2 mm×25.4 mm diameter were stamped out of the molded slabs forrheological characterization.

The test chamber of the rheometer was blanketed in nitrogen in order tominimize polymer degradation. The rheometer was preheated to the initialtemperature of the study. Upon sample loading and after oven thermalequilibration, the specimens were squeezed between the plates to a 1.6mm thickness and the excess was trimmed.

Strains were generally maintained at a single value throughout afrequency sweep but larger strain values were used for low viscositysamples to maintain a measurable torque. Smaller strain values were usedfor high viscosity samples to avoid overloading the torque transducerand to keep within the linear viscoelastic limits of the sample. Theinstrument automatically reduces the strain at high frequencies ifnecessary to keep from overloading the torque transducer. Tan δ wascalculated from the rheological measurements as the ratio of the viscousmodulus, G″, divided by the elastic modulus, G′.

E. Preparation of a Fluorided Silica-Alumina Activator-Support

The silica-alumina used to prepare the fluorided silica-alumina acidicactivator-support in this Example was typically Davison silica-aluminaobtained from W.R. Grace as Grade MS13-110, containing 13% alumina,having a pore volume of about 1.2 cc/g and a surface area of about 400m²/g. This material was fluorided by impregnation to incipient wetnesswith a solution containing ammonium bifluoride in an amount sufficientto equal 10 wt % of the weight of the silica-alumina. This impregnatedmaterial was then dried in a vacuum oven for 8 hours at 100° C. Thefluorided silica-alumina samples were then calcined. Calcination wasperformed by placing about 10 grams of the alumina in a 1.75-inch quartztube fitted with a sintered quartz disk at the bottom. While the silicawas supported on the disk, dry air was blown up through the disk at thelinear rate of about 1.6 to 1.8 standard cubic feet per hour. Anelectric furnace around the quartz tube was employed to increase thetemperature of the tube at the rate of about 400° C. per hour to a finaltemperature of about 500° C. At this temperature, the silica-alumina wasallowed to fluidize for about three hours in the dry air. Afterward, thesilica-alumina was collected and stored under dry nitrogen, and was usedwithout exposure to the atmosphere.

F. Preparation of a Sulfated Alumina Activator-Support

Sulfated alumina was formed by a process wherein alumina waschemically-treated with a sulfate or bisulfate source. Such a sulfate orbisulfate source may include, for example, sulfuric acid, ammoniumsulfate, or ammonium bisulfate.

In an exemplary procedure, a commercial alumina sold as W.R. GraceAlumina A was sulfated by impregnation with an aqueous solutioncontaining about 15-20% (NH₄)₂SO₄ or H₂SO₄. This sulfated alumina wascalcined at 550° C. in air (240° C./h ramp rate), with a 3 h hold periodat this temperature. Afterward, the alumina was collected and storedunder dry nitrogen, and was used without exposure to the atmosphere.

G. Procedures for Metallocene and Polymer Synthesis

Compounds In-1, In-2, L-5, L-6, R-1 and R-2 were prepared following theprocedure disclosed in U.S. Pat. No. 7,026,494, which is incorporated byreference in its entirety herein. Preparation procedures for thefulvenes whose chemical structures are shown below are presented in thefollowing subsections: 1 (F-1), 2 (F-2), 3 (F-3), and 4 (F-4).

After preparation, these fulvenes were used to prepare the ligands whosechemical structures are listed below, as presented in the followingsubsections: 5 (L-1), 6 (L-2), 7 (L-3), and 8 (L-4).

Procedures using ligands L-1, L-2, L-3, and L-4 to prepare the exemplarymetallocenes are presented in the following subsections: 9 (I-1), 10(I-2), 11 (I-3), and 12 (I-4). A procedure for preparing the comparativemetallocene, C-1, is presented in subsection 13. Subsection 14 disclosesthe source of the comparative commercial polyethylene samples.Subsection 15 discloses exemplary procedures for preparing polymersusing the catalyst compositions of the present techniques.

Unless specified otherwise, reagents were obtained from Aldrich ChemicalCompany and were used as received. 2,7-Di-tert-butylfluorene waspurchased from Degussa. The Grignard reagent CpMgCl (1M in THF) waspurchased from Boulder Scientific Company. Hafnium(IV) chloride andzirconium(IV) chloride were purchased from Strem. The solventtetrahydrofuran (THF) was distilled from potassium, while anhydrousdiethyl ether, dichloromethane, n-pentane, and toluene were purchasedfrom Fisher Scientific Company and stored over activated alumina. Allsolvents were degassed and stored under nitrogen. Reported preparationswere not optimized.

1. Synthesis of 2-butyl-6,6-diphenylpentafulvene (F-1)

To 1-bromobutane (34.2 g of 99 wt %, 0.247 mol) was addedcyclopentadienyl magnesium chloride (260 mL of 1 M solution in THF, 0.26mol) at 0° C. in 25 minutes. After stirring for an additional 15 minutesat 0° C., the mixture was warmed to room temperature. After stirringovernight, the reaction was quenched with a mixture of ice and water.The mixture was extracted with pentane. The organic layer was washedwith water and dried over anhydrous sodium sulfate. Removal of thesolvent under vacuum at room temperature gave a yellow liquid (30.5 g,crude butylcyclopentadiene). To the crude butylcyclopentadiene (20.5 g)dissolved in THF (150 mL) was added n-BuLi (15 mL of 10 M in hexanes,0.15 mol) at −78° C. The mixture was warmed up to room temperature andstirred for 5 hours. The anion solution was added to benzophenone (28 g,0.154 mol) dissolved in THF (100 mL) at 0° C. in 13 minutes. The mixturewas warmed to room temperature and stirred overnight. The reaction wasquenched with a mixture of ice and 10% HCl aqueous solution. The mixturewas extracted with pentane. The organic layer was washed with water anddried over anhydrous sodium sulfate. Removal of the solvent under vacuumat 40° C. gave a dark red viscous oil. The oil was dissolved in heptaneand filtered through silica gel. The product was collected by washingthe silica gel with 5-10% CH₂Cl₂ in heptane. Removal of the solvent gavethe desired product (22.3 g, 47% yield based on 1-bromobutane) as a darkred viscous oil.

2. Synthesis of 2-butyl-6,6-dimethylpentafulvene (F-2)

To 1-bromobutane (105 g, 0.766 mol) was added cyclopentadienyl magnesiumchloride (800 mL of 1M solution in THF, 0.8 mol) at 0° C. in 20 minutes.After stirring for an additional 2 hours at 0° C., the mixture waswarmed to room temperature. After stirring overnight, the reaction wasquenched with a mixture of ice and water. The mixture was extracted withpentane. The organic layer was washed with water and dried overanhydrous sodium sulfate. Removal of the solvent under vacuum at roomtemperature gave a brown liquid (85 g, crude butylcyclopentadiene). Tothe crude butylcyclopentadiene (75 g) dissolved in methanol (500 mL) wasadded acetone (54 mL) followed by pyrrolidine (63 mL) at 0° C. Themixture was warmed up to room temperature and stirred for 24 hours. Thereaction was quenched with a mixture of ice and acetic acid. The mixturewas extracted with pentane. The organic layer was washed with water anddried over anhydrous sodium sulfate. Removal of the solvent under vacuumgave the desired product (89 g) as a brown liquid.

3. Synthesis of 2-pentyl-6,6-diphenylpentafulvene (F-3)

To 1-bromopentane (109.8 g, 0.727 mol) was added cyclopentadienylmagnesium chloride (800 mL of 1M solution in THF, 0.8 mol) at 0° C. in15 minutes. After stirring for an additional 2 hours at 0° C., themixture was warmed to room temperature. After stirring overnight, thereaction was quenched with a mixture of ice and water. The mixture wasextracted with pentane. The organic layer was washed with water anddried over anhydrous sodium sulfate. Removal of the solvent under vacuumat room temperature gave a brown liquid (101.4 g, crudepentylcyclopentadiene). To the crude pentylcyclopentadiene (50 g)dissolved in THF (200 mL) was added n-BuLi (35 mL of 10 M in hexanes,0.35 mol) at 0° C. The mixture was warmed up to room temperature andstirred overnight. The anion solution was added to benzophenone (60.7 g,0.334 mol) dissolved in THF (280 mL) at 0° C. in 25 minutes. The mixturewas warmed to room temperature and stirred overnight. The reaction wasquenched with a mixture of ice and 10% HCl aqueous solution. The mixturewas extracted with pentane. The organic layer was washed with water anddried over anhydrous sodium sulfate. Removal of the solvent under vacuumat 50° C. gave a dark red viscous oil. The oil was dissolved in heptaneand filtered through silica gel. The product was collected by washingthe silica gel with 5-10% CH₂Cl₂ in heptane. Removal of the solvent gavethe desired product (74.3 g) as a dark red viscous oil.

4. Synthesis of 6,6-diphenylpentafulvene (F-4)

Benzophenone (63.8 g, 350 mmol) was dissolved in anhydrous1,2-dimethoxyethane (DME) (150 mL) under nitrogen. In a one-liter flask,ground potassium hydroxide (30 g, 535 mmol) was slurried in DME (200mL). The slurry was cooled in an ice bath and freshly crackedcyclopentadiene (35 mL, 430 mmol) was added. After 30 minutes, thesolution of benzophenone was added over 15 minutes. The flask wasstirred in a refrigerator for 90 hours and then, while cooling in ice,3M HCl (450 mL) was added. The mixture was diluted with pentane (500 mL)and separated. The organic layer was washed with water (2×200 mL) anddried over sodium sulfate. The solution was filtered and taken todryness under vacuum. The solid was dissolved in boiling pentane (600mL) and then concentrated to 400 mL. Cooling to −15° C. for 40 hoursgave a red solid (69.5 g, 86.3% yield). (F-4 may also be commerciallyavailable from Sigma-Aldrich).

5. Synthesis of1-(3-butylcyclopentadien-1-yl)-1-(2,7-di-tert-butylfluoren-9-yl)-1,1-diphenylmethane(L-1)

To 2,7-di-tert-butylfluorene (15 g, 54 mmol) dissolved in Et₂O (100 mL)was added n-BuLi (5.8 mL of 10 M in hexanes, 58 mmol) at 0° C. Themixture was warmed to room temperature and stirred overnight. The anionsolution was added to 2-butyl-6,6-diphenylpentafulvene (F-1) (16 g, 56mmol) dissolved in Et₂O (100 mL) at −78° C. in 5 minutes. The mixturewas warmed to room temperature and stirred for 2 days. The reaction wasquenched with a mixture of ice and 10% HCl aqueous solution. The mixturewas extracted with Et₂O. The organic layer was washed with water anddried over anhydrous sodium sulfate. Removal of the solvent under vacuumgave a viscous oil. The oil was stirred in heptane to give a whitesolid. The solid was filtered, washed with heptane and dried undervacuum. A mixture of isomers for the desired product (18.7 g, 61.3%yield) was obtained as a white solid.

6. Synthesis of1-(3-butylcyclopentadien-1-yl)-1-(2,7-di-tert-butylfluoren-9-yl)-1,1-dimethylmethane(L-2)

To 2,7-di-tert-butylfluorene (27.8 g, 100 mmol) dissolved in Et₂O (200mL) was added n-BuLi (11 mL of 10 M in hexanes, 110 mmol) at 0° C. Themixture was warmed to room temperature and stirred overnight. To theanion solution was added to 2-butyl-6,6-dimethylpentafulvene (F-2) (20g, 123 mmol) at −78° C. in less than one minute. The mixture was warmedto room temperature and stirred overnight. The reaction was quenchedwith a mixture of ice and saturated NH₄Cl aqueous solution. The mixturewas extracted with Et₂O. The organic layer was washed with water anddried over anhydrous sodium sulfate. Removal of the solvent under vacuumgave a viscous oil. The oil was dissolved in heptane and purifiedthrough silica gel column with 5-10% CH₂Cl₂ in heptane. A mixture ofisomers for the desired product (33.8 g, 76.8% yield) was obtained as aviscous oil.

7. Synthesis of1-(3-pentylcyclopentadien-1-yl)-1-(2,7-di-tert-butylfluoren-9-yl)-1,1-diphenylmethane(L-3)

To 2,7-di-tert-butylfluorene (18 g, 64.7 mmol) dissolved in Et₂O (100mL) was added n-BuLi (6.8 mL of 10 M in hexanes, 68 mmol) at 0° C. Themixture was warmed to room temperature and stirred overnight. The anionsolution was added to 2-pentyl-6,6-diphenylpentafulvene (F-3) (20 g, 67mmol) dissolved in Et₂O (100 mL) at −78° C. in 2 minutes. The mixturewas warmed to room temperature and stirred for 2 days. The reaction wasquenched with a mixture of ice and 10% HCl aqueous solution. The mixturewas extracted with Et₂O. The organic layer was washed with water anddried over anhydrous sodium sulfate. Removal of the solvent under vacuumgave a viscous oil. The oil was stirred in heptane to give a whitesolid. The solid was filtered, washed with heptane and dried undervacuum. A mixture of isomers for the desired product (22.7 g, 60.7%yield) was obtained as a white solid.

8. Synthesis of1-(cyclopentadien-1-yl)-1-(2,7-di-tert-butylfluoren-9-yl)-1,1-diphenylmethane(L-4)

To a solution of 2,7-di-tert-butylfluorene (29.8 g, 107 mmol) in drytetrahydrofuran (THF) (100 mL), cooled in dry ice, was added n-BuLi(43.0 mL of 2.5 M in hexanes, 107.5 mmol). The bath was removed and thedark solution was stirred for 2 hours. This solution was then addeddropwise to a solution of 6,6-diphenylpentafulvene (F-4) (26.0 g, 113mmol) in THF (100 mL), while cooling in ice. The reaction mixture wasstirred at room temperature for 86 hours and then cooled in ice. 1M HClsolution, (100 mL) was added. The mixture was diluted with chloroform(100 mL) and separated. The chloroform layer was washed with water(3×100 mL) and dried over sodium sulfate. The solution was filtered andevaporated to a light orange solid. The solid was dissolved in boilingchloroform (150 mL) and methanol (150 mL) was slowly added. Aftercooling for two days to −15° C., the solid was filtered off, ground, anddried under vacuum. The desired product (25.4 g, 46.7% yield) wasobtained as an off white solid.

9. Synthesis of[1-(η⁵-3-butylcyclopentadien-1-yl)-1-(η⁵-2,7-di-tert-butylfluoren-9-yl)-1,1-diphenylmethane]hafniumdichloride (I-1 in FIG. 1)

To1-(3-butylcyclopentadienyl)-1-(2,7-di-tert-butylfluorenyl)-1,1-diphenylmethane(L-1) (6.7 g, 11.9 mmol) dissolved in Et₂O (60 mL) was slowly addedn-BuLi (2.6 mL of 10 M in hexanes, 26 mmol) at 0° C. The mixture waswarmed to room temperature, stirred overnight, and then added viacannula to HfCl₄ (4.2 g, 13 mmol) suspended in a mixture of pentane (60mL) and Et₂O (10 mL) at 0° C. The mixture was warmed to roomtemperature, stirred overnight, and evacuated to dryness. The residuewas stirred in pentane (50 mL) and centrifuged. The supernatant wasdiscarded. The remaining solid was washed a second time with pentane (30mL), then extracted with methylene chloride and centrifuged. Thesolution was taken to dryness under vacuum to give a yellow solid (6.7g, 69.4% yield).

10. Synthesis of[1-(η⁵-3-butylcyclopentadien-1-yl)-1-(η⁵-2,7-di-tert-butylfluoren-9-yl)-1,1-diphenylmethane]zirconiumdichloride (I-2 in FIG. 1)

To1-(3-butylcyclopentadienyl)-1-(2,7-di-tert-butylfluorenyl)-1,1-diphenylmethane(L-1) (7.9 g, 14 mmol) dissolved in Et₂O (70 mL) was slowly added n-BuLi(3 mL of 10 M in hexanes, 30 mmol) at 0° C. The mixture was warmed toroom temperature, stirred overnight, and then added via cannula to ZrCl₄(3.43 g, 14.7 mmol) suspended in a mixture of pentane (70 mL) and Et₂O(10 mL) at 0° C. The mixture was warmed to room temperature, stirredovernight, and evacuated to dryness. The residue was stirred in pentane(100 mL) and centrifuged. The supernatant was discarded. The remainingsolid was washed a second time with pentane (50 mL), then extracted withmethylene chloride and centrifuged. The solution was taken to drynessunder vacuum to give an orange solid (7 g, 69.3% yield).

11. Synthesis of[1-(η⁵-3-butylcyclopentadien-1-yl)-1-(η⁵-2,7-di-tert-butylfluoren-9-yl)-1,1-dimethylmethane]zirconiumdichloride (I-3 in FIG. 1)

To1-(3-butylcyclopentadienyl)-1-(2,7-di-tert-butylfluorenyl)-1,1-dimethylmethane(L-2) (12 g, 27.3 mmol) dissolved in Et₂O (150 mL) was slowly addedn-BuLi (6 mL of 10 M in hexanes, 60 mmol) at 0° C. The mixture waswarmed to room temperature, stirred overnight, and then added viacannula to ZrCl₄ (7 g, 30 mmol) suspended in a mixture of pentane (150mL) and Et₂O (10 mL) at 0° C. The mixture was warmed to roomtemperature, stirred overnight, and evacuated to dryness. The residuewas stirred in pentane (100 mL) and centrifuged. The supernatant wasdiscarded. The remaining solid was washed a second time with pentane(100 mL), then extracted with methylene chloride and centrifuged. Thesolution was taken to dryness under vacuum to give a red solid (11.8 g,72% yield).

12. Synthesis of[1-(η⁵-3-pentylcyclopentadien-1-yl)-1-(η⁵-2,7-di-tert-butylfluoren-9-yl)-1,1-diphenylmethane]zirconiumdichloride (I-4 in FIG. 1)

To1-(3-pentylcyclopentadienyl)-1-(2,7-di-tert-butylfluorenyl)-1,1-diphenylmethane(L-3) (8 g, 13.8 mmol) dissolved in Et₂O (70 mL) was slowly added n-BuLi(3 mL of 10 M in hexanes, 30 mmol) at 0° C. The mixture was warmed toroom temperature, stirred overnight, and then added via cannula to ZrCl₄(3.4 g, 14.7 mmol) suspended in a mixture of pentane (70 mL) and Et₂O(10 mL) at 0° C. The mixture was warmed to room temperature, stirredovernight, and evacuated to dryness. The residue was stirred in pentane(50 mL) and centrifuged. The supernatant was discarded. The remainingsolid was washed a second time with pentane (50 mL), then extracted withmethylene chloride and centrifuged. The solution was taken to drynessunder vacuum to give an orange solid (6.9 g, 73.5% yield).

13. Synthesis of[1-(η⁵-cyclopentadien-1-yl)-1-(η⁵-2,7-di-tert-butylfluoren-9-yl)-1,1-diphenylmethane]zirconiumdichloride (C-1 in FIG. 2)

Under nitrogen,1-cyclopentadienyl-1-(2,7-di-tert-butylfluorenyl)-1,1-diphenylmethane(L-4) (15.26 g, 30.0 mmol) was suspended in dry Et₂O (250 mL). Whilecooling in dry ice, n-BuLi (24.0 mL of 2.5 M in hexanes, 60 mmol) wereadded dropwise. The bath was then removed and the mixture was stirredfor 24 hours. The solution was gradually added to zirconiumtetrachloride (7.38 g, 31.7 mmol) suspended in pentane (50 mL) andcooled in ice. The orange slurry was stirred for 90 hours and allowed towarm to room temperature. The resulting slurry was centrifuged and thesolid was mixed with dry methylene chloride (120 mL). The mixture wascentrifuged and the solution was removed and taken to dryness undervacuum. The desired product (9.63 g, 48% yield) was obtained as anorange solid.

14. Commercial Polyethylene Samples

Commercial polyethylene resins, as shown in Examples 19-24 in Table 3,were analyzed to determine Tan δ and molecular weight properties forcomparison to Examples 3-15 given in Table 2. These resins were preparedusing commercial chromium catalyst systems. All of the resins tested areavailable from Chevron Phillips Chemical Company under the productnumbers shown in the column entitled “Commercial Resin.”

15. Polymerization Procedures for Examples 1-18

Examples 1-18 in Tables 1 and 2 illustrate ethylene polymerization runsperformed in a one-gallon (3.785 liter) stainless steel autoclavereactor at various temperatures, using two liters of isobutane diluentand an aluminum alkyl cocatalyst and scavenger. No hydrogen or comonomerwas added. Metallocene solutions (2 mg/mL) were typically prepared bydissolving 30 mg of the metallocene in 15 mL of toluene. A typicalpolymerization procedure is as follows. The aluminum alkyl compound,treated solid oxide, and the metallocene solution were added through acharge port, typically in that order, while venting isobutane vapor. Thecharge port was closed and two liters of isobutane were added. Thecontents of the reactor were stirred and heated to the desired runtemperature. Ethylene was fed on demand to maintain the specifiedpressure for the specified length of the polymerization run. The reactorwas maintained at the desired run temperature through the run by anautomated heating and cooling system.

After the allotted polymerization time, the ethylene flow was stopped,and the reactor slowly depressurized and opened to recover a granularpolymer. In all cases, the reactor was clean with no indication of anywall scale, coating or other forms of fouling. The polymer was thenremoved and weighed, giving the results listed in Tables 1 and 2, above.

While the techniques presented herein may be susceptible to variousmodifications and alternative forms, specific embodiments have beenshown by way of example in the drawings and have been described indetail herein. However, it should be understood that the invention isnot intended to be limited to the particular forms presented. Rather,the invention is to cover all modifications, equivalents andalternatives falling within the spirit and scope of the invention asdefined by the following appended claims.

What is claimed is:
 1. An ansa-metallocene comprising a compound havingthe formula:

wherein: M¹ is zirconium or hafnium; X′ and X″ are independently F, Cl,Br, I, H, BH₄, methyl, phenyl, benzyl, neopentyl, trimethylsilylmethyl,CH₂CMe₂Ph, CH₂SiMe₂Ph, CH₂CMe₂CH₂Ph, or CH₂SiMe₂CH₂Ph; E is C or Si; R¹and R² are independently an alkyl group, an aryl group, or hydrogen;R^(3A) and R^(3B) are independently a hydrocarbyl group, atrihydrocarbylsilyl group, or hydrogen; n is an integer from 0 to 10,inclusive; and R^(4A) and R^(4B) are independently a hydrocarbyl group.2. The ansa-metallocene of claim 1, wherein X′ and X″ are independentlyF, Cl, Br, or I.
 3. The ansa-metallocene of claim 2, wherein R^(3A) andR^(3B) are independently the hydrocarbyl group or thetrihydrocarbylsilyl group, and wherein the hydrocarbyl group or thetrihydrocarbylsilyl group have up to 20 carbon atoms.
 4. The method ofclaim 2, wherein R^(3A) and R^(3B) are independently H, methyl, allyl,ethyl, propyl, benzyl, butyl, pentyl, hexyl, or trimethylsilyl.
 5. Theansa-metallocene of claim 4, wherein n is an integer from 1 to 6,inclusive.
 6. The ansa-metallocene of claim 4, wherein R^(4A) and R^(4B)are independently a hydrocarbyl group having up to 6 carbon atoms. 7.The ansa-metallocene of claim 2, wherein R¹ and R² are independentlymethyl or phenyl.
 8. The ansa-metallocene of claim 2, wherein R^(3A) andR^(3B) are independently H or methyl.
 9. The ansa-metallocene of claim2, wherein n is 1 or
 2. 10. The ansa-metallocene of claim 2, whereinR^(4A) and R^(4B) are independently H or t-butyl.
 11. Theansa-metallocene of claim 1, wherein X′ and X″ are independently H, BH₄,methyl, phenyl, benzyl, neopentyl, trimethylsilylmethyl, CH₂CMe₂Ph,CH₂SiMe₂Ph, CH₂CMe₂CH₂Ph, or CH₂SiMe₂CH₂Ph.
 12. A method of producing anansa-metallocene, comprising: reacting an ansa-metallocene ligand havingthe formula:

 with a base to generate a respective intermediate; and reacting therespective intermediate with ZrCl₄ to generate the ansa-metallocenehaving the formula:

 or reacting the respective intermediate generated by the reactionbetween the base and the ansa-metallocene ligand, wherein theansa-metallocene ligand has the formula:

 with HfCl₄ to generate the ansa-metallocene having the formula:


13. The method of claim 12, wherein the ansa-metallocene ligand has theformula:


14. The method of claim 13, comprising generating the ansa-metalloceneligand from a reaction involving a fulvene and2,7-di-tert-butylfluorene, and wherein the fulvene has the formula:


15. The method of claim 12, wherein the ansa-metallocene ligand has theformula:


16. The method of claim 15, comprising generating the ansa-metalloceneligand from a reaction involving a fulvene and2,7-di-tert-butylfluorene, and wherein the fulvene has the formula:


17. The method of claim 12, wherein the ansa-metallocene ligand has theformula:


18. The method of claim 17, comprising generating the ansa-metalloceneligand from a reaction involving a fulvene and2,7-di-tert-butylfluorene, and wherein the fulvene has the formula:


19. An ansa-metallocene ligand comprising a compound having the formula:

wherein: E is C or Si; R¹ and R² are independently an alkyl group, anaryl group, or hydrogen; R^(3A) and R^(3B) are independently ahydrocarbyl group, a trihydrocarbylsilyl group, or hydrogen; n is aninteger from 0 to 10, inclusive; and R^(4A) and R^(4B) are independentlya hydrocarbyl group.
 20. An ansa-metallocene having a formula of: